Abstract: COVID-19 has drawn greater attention to the prospect of biological weapons use. But when it comes to bioterrorism, the pandemic probably has not moved the needle much. Although COVID-19 might encourage apocalyptic cults, some radical environmentalists, some extreme right-wing groups, and some Islamist extremist groups toward biological weapons, most other terrorist groups are more likely to be discouraged. The pandemic has bolstered some terrorists’ bio-related capabilities but in at most modest ways. At the same time, lessons from the COVID-19 experience may both help reduce the consequences of a future attack and heighten perceptions of bioterrorism risk. Fundamentally, bioterrorism has to date been rare, and even after COVID-19, it is likely to remain so. Even if the threat of bioterrorism might increase due to technological and other dynamics, this trajectory appears unlikely to be appreciably affected by the COVID-19 pandemic.

The COVID-19 pandemic provided a stark reminder of the potential damage that biological agents can wreak on society. Over a million people have died from the disease in the United States alone. The International Monetary Fund estimated COVID-19 “will cost the global economy $12.5 trillion through 2024.”1 The pandemic even emphasized that the world’s militaries are vulnerable to disease as well, for example when the USS Theodore Roosevelt evacuated most of its crew because of a severe COVID outbreak.2

COVID-19 has also raised larger fears about the future of biological warfare: If a naturally occurring pandemic can cause so much harm, what about a human-engineered one? After all, adversaries, both state and non-state, have been using biological organisms or their products to harm one another for thousands of years.3 Given the inordinate global harm, bad actors might be expected to scramble to acquire such weapons in hopes of visiting this level of destruction on their adversaries. And at the forefront of this group would presumably be terrorist groups and individuals who, as consummate asymmetric actors, would surely not be able to resist the clarion call of the microbe. While pursuit of large-scale, sophisticated biological weapons only took off in the 20th century, concerns about bioterrorism really only began to arise in the 1990s.

The implications of COVID-19 for bioterrorism appear complex and contingent. For example, terrorist ideology acts as a critical mediating factor. While the COVID-19 experience might encourage certain groups with apocalyptic goals to pursue biological weapons, it might equally discourage groups with narrower goals that recognize widespread harm might result in significant blowback both upon and from their own supporters. Indeed, it probably does little to energize actors who were already oriented toward bioterrorism, besides educating them on some key nuances, including the difficulty of controlling the outcomes when using contagious bioagents. In general, the authors assess COVID-19 will have a limited overall effect on bioterrorism risks, though it may have greater effects on perceptions of those risks.

For government agencies concerned with bioterrorism, this therefore suggests that fundamental changes in their risk assessments or countermeasures are likely not needed. Counterterrorism efforts should largely continue to focus on the same set of pre-COVID-19 actors and threats (including the impact of emerging technologies). Two possible, additional recommendations are: a heightened focus on groups holding ideologies of an apocalyptic-millenarian character, and to direct specific intelligence collection and analysis efforts toward regions where extremists might exploit new vaccine development capacity to develop capabilities related to handling pathogenic agents. Agencies should also support broader efforts for resilience against disease generally as responding to man-made pandemics is not likely to be drastically different than responding to natural ones.

To unpack this argument, the authors first construct a schema for bioterrorism, which identifies the main categories of threat actors and threat vectors. This provides a baseline of pre-COVID assessments of the bioterrorism threat and how bioterror risks vary considerably between actors and vectors. Then the authors use this schema as a basis for considering the changes wrought by COVID-19 and situating the pandemic’s effects on different areas of bioterrorism risk. The article concludes with several policy recommendations.

What’s What: Creating a Taxonomy of Bioterrorism
By bioterrorism, the authors are referring to terrorist actsa involving pathogenic microorganisms or biological toxins (complex, toxic molecules produced by living organisms). Although the scope of this article precludes a comprehensive survey of bioterrorism,4 the authors will note some key features of the topic that are pertinent to the creation of a practical taxonomy, which can then be used to explore changes in the threat over time, specifically from before to after the COVID-19 pandemic.

First, bioterrorism is extremely rare within the annals of terrorism. Of the more than 200,000 terrorist events between 1970 and 2019 contained in the Global Terrorism Database, only 38 (0.02 percent) are listed as involving biological weapons.5 This (fortunate) infrequency means that the empirical basis for constructing a taxonomy is limited. In addition, the current effort is intended to be more than merely a record of the past, but to enable forward-looking analyses of a highly dynamic context where technologies are advancing rapidly and adversaries are constantly adapting. For these reasons, a strict taxonomic approach is insufficient here and must be accompanied by typological elements.b The resulting classification schema is informed wherever possible by the (relatively meager) empirical record of bioterrorism, primarily drawn from the Profiles of Incidents involving CBRN and Non-state Actors (POICN) Database, which as of its latest update in 2017 contains 107 bioterrorist incidents.6 c It is supplemented where necessary with conceptually determined categories that encompass potential future threats. The authors label the resulting classification as the Bioterrorism Classification Schema.

The Bioterrorism Classification Schema (BTCS) is based on a standard risk construction of viewing threat as a combination of an adversary’s intent and capability. It also takes into account both the threat actor (the individual or group seeking to perpetrate the bioterrorist attack) and the threat vector (the means by which the attack is perpetrated using a biological agent). With respect to the number of categories needed, the authors attempt to capture most of the historically and theoretically relevant categories, while at the same time seeking to prevent the framework from becoming too unwieldy for practical analytical usage. As a result, where two potential categories are determined to be more reasonably similar, then those categories are merged into one, unless there is a compelling conceptual reason not to do so.

Threat actor was defined mostly in accordance with the POICN database, with some minor modifications to better match the needs of the study. The intent to engage in bioterrorism varies more according to the threat actor’s underlying motivation (ideology or cause),d while levels of capability vary more according to the organizational structure of the threat actor.e Of course, in practice, motivation and capability are not empirically or theoretically independent: Ideological groups may have different distributions of group capabilities, while ideology may support or detract from acquiring specific or general capabilities.

The authors chose motivation categories based on those of the known perpetrators listed in the POICN database. After placing animal rights and other environmental extremists into a single category for simplicity,f this yields seven categories: Islamist extremist, apocalyptic/millenarian cults, ethno-nationalist, extreme far-right, extreme far-left, animal rights/environmentalism, and idiosyncratic objective.g The last category is not incorporated directly into the schema, but needs to be assessed separately in each case (see Box 1).

Box 1: Idiosyncratic Perpetrators
Certain perpetrators (primarily lone actors) can have a variety of idiosyncratic motives for engaging in violence, arising from nurturing a personal or professional grudge and/or suffering from delusional mental illness. These are not an insignificant proportion of perpetrators, with such idiosyncratic motives being present in roughly 17 percent of recorded bioterrorism incidents in POICN7 and among 23 percent of past non-state biological perpetrators in a related actor-level database.8 However, owing to the wide variation in possible causes and forms such motives can take, it is far more difficult to apply even moderately consistent values to the motivation portions of the schema across the various agents. The authors therefore cannot include actors with idiosyncratic motivations in the BTCS in the same way as other motivational types. Nonetheless, some guidance regarding these actors’ bioterrorism decision-making is available. For example, in a study of the psychology of chemical and biological perpetrators, it was found that those with an idiosyncratic motive are most likely to attack individuals and to use food or product contamination (27 of 51 cases).9 Overall, when evaluating the motivational component of the schema for idiosyncratic actors, therefore, the specific psychological circumstances of the individual and the nature of the idiosyncratic belief system should be taken into account in assessing likely agent and delivery system selection.

When considering capability, the POICN database uses three categories of organizational structure: lone actor, small cell, and formal terrorist organization. Given recent geostrategic developments that suggest cash-strapped states could sell arms to terrorists10 and considering that states have access to resources and capabilities that even the most advanced terrorist groups do not, the authors added another category at the high end of the capability spectrum for state-sponsored terrorist groups (though the economic pressures of COVID-19 may decrease the general financial support state sponsors provide to terrorist groups). In addition, the authors add a lone actor “rogue scientist”/insider category to capture the possibility of a highly knowledgeable individual with a minimal support network. Such a knowledgeable individual may also be a part of a small cell, formal terrorist group, or state-sponsored group, but this is not typical.h

With respect to threat vector, a weapon system consists of a harm agent together with the means to deliver said agent to the target(s), the delivery mechanism being especially relevant in the case of non-contagious biological weapons.i Therefore, the authors consider two separate components of the threat vector: 1) the acquisition, culturing, and preparation of the bioagent (pathogen or toxin), as well as 2) the dissemination mechanism. The authors distinguish between three categories of agent acquisition/production: a) crude agents requiring little to no formal biological training and no specialized equipment to acquire or produce, b) agents requiring moderate levels of training and some specialized equipment, and c) sophisticated agents requiring extensive expertise and high-end equipment. Examples of bioagents that fall into each of these categories are given in Table 1. Given the objective of assessing changes wrought by COVID-19, a highly contagious agent, the authors further subdivide the bioagent category into contagious versus non-contagious agents. This differs somewhat from typical military or CDC categorizations.

In traditional military contexts, bioagents are usually categorized according to the biological family of the agent (bacterium, virus, protozoa, toxin, etc.). This makes sense when the adversaries concerned are all states with a sizable resource base that would not normally intentionally seek to produce crude agents of low quality. Terrorists, however, often have a wider range of operational objectives and greater resource constraints, so the nuances of viral as opposed to bacterial agent production are less informative than the overall sophistication required for preparation of the agent and the quality (in terms of survivability,j infectiousness, dispersibility, etc.) of the resulting product. Similarly, while the CDC has published a list of Category A, Category B, and Category C agents,11 these categories are at least partially based on the characteristics of the disease the agent causes (such as its morbidity, mortality, and infectious dose), and were designed to guide the levels of security and safety required for legitimate work with each agent. While incorporating the ease of dissemination and production of agents, the CDC categories are not designed to cover the entire range of agent preparations that terrorists might pursue, which have historically often been rather low-level, often involving agents (like abrin or HIV) that do not even appear on the CDC lists.12 At the same time, much of the concern with respect to bioterrorism lies in the potential dangers posed by high-end emerging technologies,13 especially the burgeoning fields of synthetic biologyk (encompassing such advances as the CRISPR-Cas9 method of targeted genome editing, rapid DNA synthesis and genome transplantation technologies) and new delivery technologies (such as microencapsulation and bacteriophages14), which are not covered in these existing categorizations.

For delivery mechanism categories, the authors draw on the empirical record in POICN, as well as delivery mechanisms used in the history of biological warfare; the authors combine several POICN categories for simplification while preserving the essential features of each delivery method. The categories are also intentionally cast sufficiently broadly so as to allow for the inclusion of emerging technologies. For example, drone swarms as delivery platforms15 could be included as a subcategory of Aerosol/Sprayl delivery mechanisms, and a wide range of munitions ranging from mortars to cluster bombs can be included under the Explosive category. This leads to seven possible categories: Aerosol/Spray, Direct Contact/Latent,m Food/Product Contamination, Explosive, Animal Vector, Mail, and Water Supply.

Table 1 depicts the completed Bioterrorism Classification Schema matrix. Individual cells have been populated with a simple five-scaled measure of “Very Low,” “Low,” “Medium,” “High,” or “Very High” to denote the relative likelihood of the particular threat actor having the intention or capability to successfully pursue a given threat vector (agent or delivery mechanism). These values reflect the threat just prior to the outbreak of the COVID-19 pandemic at the end of 2019. The metrics used, however, are not integral to the structure of the Bioterrorism Classification Schema, and future efforts can replace the current measure with a more complex construction. It should also be noted that to thoroughly determine the value for each cell of the Bioterrorism Classification Schema would require a degree of analysis (both empirical and deductive) that is beyond the scope of this paper.n However, it is not strictly necessary to do so for the authors’ current purpose, since the structure of the matrix itself allows for systematic consideration of which elements are likely to be affected by the COVID-19 pandemic and whether they are likely to increase or decrease. Nonetheless, preliminary values for each cell have been estimated, based on the authors’ expertise studying bioterrorism and its perpetrators, descriptive empirical information obtained directly from the POICN database, and other results drawn from the literature. Furthermore, while a rigorous threat assessment is not the focus of this article, some illustrative worked examples of how the Bioterrorism Classification Schema can be utilized to estimate the threat of particular bioterrorism scenarios are provided in the appendix.o

Although the authors are not seeking to provide rigorous justifications for each of the individual likelihood values in the Bioterrorism Classification Schema, they offer several observations to demonstrate that the Bioterrorism Classification Schema largely concurs with the pre-COVID-19 expert consensus with respect to bioterrorism:

  • The matrix shows not all terrorists will seek to utilize bioterrorism to cause mass death, or even mass casualties.16 The motive for the case of the Rajneeshee cult in Oregon in 1984 was merely to prevent people from voting in a local election,17 while at least part of the objective for sending the 2001 “anthrax letters” in the United States was to leverage the natural human fear of disease and doubt regarding exposure to inflict psychological harm and social disruption. Therefore, several threat actors in the Bioterrorism Classification Schema are estimated to have a fairly high likelihood of pursuing the use of rather crude agents.
  • The Bioterrorism Classification Schema overall reflects the widely proffered dynamic that the more sophisticated the bioagent and/or delivery system is, the less likely any given actor will possess or be able to acquire the capability to effectively deploy it.18
  • Both older and more recent studies suggest that religiously motivated terrorists in general, and Islamist terrorists in particular, have the highest overall motivation to engage in bioterrorism,19 p while apocalyptic millenarian cults (like the erstwhile Aum Shinrikyo) probably have the highest interest in high-end biological weapons specifically.20 q
  • The moderate interest shown by ethno-nationalist groups in low-moderate level bioterrorist attacks and the lower overall interest of extreme far-left organizations reflect the empirical record in POICN, while the atypical, somewhat elevated interest of the animal rights/environmentalist milieu in specific agents and delivery systems is drawn from various theoretical analyses.21
  • The relatively greater values across threat actors for crude non-contagious and moderate non-contagious agents (which include ricin and botulinum toxin, respectively) reflect the high frequency of use for these agents.r
  • The estimates of delivery mechanism selection likelihoods are mostly drawn from POICN; for example, the observation that the contamination of food and consumer products has traditionally been among the more commonly attempted and successful delivery methods, while only Islamist extremist and ethno-nationalist groups have attempted to utilize explosives to disseminate bioagents. This is supplemented with theoretical arguments and broader tactical records where these are relevant, such as when extreme far-right groups were assigned a higher likelihood of attacking the water supply.s
  • Capability likelihoods were similarly derived from POICN and shaped by the results of prior analyses. For example, they reflect the findings that lone actors are particularly adept at using biological agents (albeit at the less sophisticated end of the spectrum)t and that existing published manuals indicate a continued low-level competency to enact sophisticated or large-scale bioterrorist attacks.22 The absence of any evidence of a successful mass-casualty bioterrorist attack using contagious agents and only 11 small-scale incidents occurring since 2012 demonstrate the difficulty of acquiring a viable capability for all but the crudest bioweapons and smaller-scale attacks.23 Concerns regarding the provision of bioweapons from state-run programs,24 the singular capabilities of technically proficient insiders,25 and the facilitating effects of emerging technologies such as CRISPR-Cas9 and biotechnology “kits,”26 are also reflected in the matrix.
COVID-19 Coronavirus molecule, March 24, 2020 (CDC/API/Gamma-Rapho via Getty Images)

The Effects of COVID-19 on Bioterrorism
The effects of COVID-19 on bioterrorism risk can be considered across three general aspects: (a) terrorist interest in bioterrorism; (b) capabilities of terrorist groups to carry out bioterrorism; and (c) impacts on the consequences of bioterrorism. There is also a fourth, more abstract but still meaningful impact on how policy makers and the policy intelligentsia think about bioterrorism risk, with it being possible that (d) COVID-19 impacts threat assessment more than it impacts the threat itself. The changes relating to (a) and (b) are summarized in Table 2.

a) COVID-19 will probably boost interest in biological weapons among terrorist groups with maximalist ideologies, but decrease it for others.
The COVID-19 pandemic clearly illustrates the significant, global harm a contagious biological weapon could cause. A typical terror attack using guns or even bombs might kill a handful of people; a complex, sophisticated attack like the 9/11 attacks can kill thousands; but a COVID-like biological weapon might kill millions. Given the extreme way COVID-19 has spread throughout the world, disrupted most aspects of society, and captured global attention, COVID-19 undoubtedly encouraged many terrorist groups to at least consider biological weapons. The question remains, though: Do terrorists perceive such extreme harm as a good thing? And how does the prospect of indiscriminate, potentially uncontrollable, mass harm fit into their broader ideology, strategies, and goals?

Groups with maximalist ideologies aiming for drastic, global, or even cosmic change such as apocalyptic cults, some extreme environmental groups,u or accelerationist extreme right-wing groups27 necessarily require extreme means to achieve their goals. While a handful of attacks aimed at garnering public attention and perhaps support may help, drastic ends require drastic means, especially for more misanthropic ideologies. Biological weapons are one of the few avenues available to cause globally catastrophic, and especially existential, harm. For example, the green anarchist group RISE in 1970s Chicago sought biological weapons as a way to kill off most of humanity to repopulate the Earth with enlightened environmentalists.28 COVID-19’s impacts on the motivations of such groups might also not manifest in the short-term. After all, groups with such apocalyptic ideologies are relatively rare, and even rarer still are those with meaningful capabilities. Decades from now, however, some future apocalyptic extremist group may look back at the COVID-19 pandemic as evidence of the potential utility of biological weapons.

However, groups with narrower objectives or even ambitious, but not global, goals may see the harm as a strong reason not to pursue biological weapons, or at least not contagious biological weapons whose effects are difficult to either gauge or control. COVID-19 killed millions, but it was relatively indiscriminate in doing so. COVID-19 spread throughout the world, with major outbreaks in virtually every country. People, especially those in big cities, were infected, regardless of race, class, gender, religion, and political ideology (though exact infection and mortality rates do differ across these demographics). A group using a contagious biological weapon would have to accept significant potential risk of infecting, and killing, their own real and potential supporters.v Even for contagious diseases that spread less readily than the SARS-CoV-2 virus has, a would-be bioterrorist cannot comfortably predict which communities the disease will spread to, and which it will not.

So, the pandemic is unlikely to cause a disinterested ideological group to strongly favor bioterrorism post-pandemic (e.g., a change from low to high motivation for carrying out a bioterrorism attack), or similar dramatic changes in motivations for bioterrorism overall. A subset of the already-small subset of groups with maximalist aims that were not already interested in biological weapons might view the effects of the pandemic and be more attracted to the ability of bioagents to spread indefinitely and sicken millions. For the remainder of terrorist groups, the pandemic seems likely to disincentivize the use of contagious bioagents at the very least. As for non-contagious bioagents, the pandemic should have minimal impact: Those already interested in non-contagious agents pre-COVID-19 will likely remain interested, while the contagious nature of the pandemic means that it does not present other terrorists with any advantageous lessons that might make them more interested in non-contagious agents.

b) COVID-19’s effects on terrorist bioterrorism capability are likely modest at most.
The COVID-19 pandemic is likely to have at most modest impacts on terrorists’ capabilities to conduct bioterrorism. Terrorists generally have been affected by the pandemic, too, so some of them will have been “calling in sick,” or even dying, thus reducing the operational capabilities of those groups, at least temporarily (the exception is groups in conflict zones where there appears to be no reduction in terrorist activity).29 On the other hand, the downtime from lockdowns and the inability to continue normal operations might provide time and space to focus on building organizational and operational capabilities that could manifest in attacks down the road.30 The same dynamics potentially apply to bioterrorism.

Terrorists and other actors might seek, and in some cases already have sought, to weaponize the coronavirus that causes COVID-19.31 These appear often to be small-scale, opportunistic attempts to spread the disease through casual or personal contact, which may support the general spread of disease but not create a major unique effect. As such, terrorist efforts have to date and are likely in the future to have at most modest consequences on the course of the disease, especially given the increasing availability of vaccines and treatments. Potential attacks utilizing COVID-19 are only likely to have noticeable effects in areas with low prior exposure to the disease, lower vaccination rates, or if a new strain emerges that is not susceptible to current vaccines, although all of these circumstances provide terrorists with only a limited window for action.32

The massive increase in medical and public health resources as a result of the pandemic might also create new opportunities for terrorists to exploit in the medium- to long-term. For example, new laboratories built in response to the pandemic might provide new opportunities for stealing pathogens or for radicalized insiders to build technical skills.33 Likewise, even though the pandemic likely curtailed academic teaching and research laboratories in the short-term, the spread of vaccination efforts and efforts to achieve rapid up-skilling in related medical expertise, particularly in the global South,34 may support the proliferation of knowledge necessary to create and disseminate biological weapons agents. That is, gaining comfort and expertise with handling and manipulating contagious pathogens in general can be applied to handling and manipulating contagious pathogens intended for bioterrorism. However, the magnitude of this knowledge transfer should not be overstated, because even if a would-be bioterrorist were provided with this knowledge and skill, they are unlikely to cover the full biological weapons acquisitions cycle. That is, a rapidly trained virologist or vaccine production technician has no need to learn the technical details of weaponizing and disseminating a biological weapons agent en masse, even if they had access to the technical resources to do so.

To the extent that state sponsors provide witting aid to terrorists, COVID-19 might influence states’ motivations to aid terrorists and what they have to offer them. The pandemic could both increase and decrease states’ motivations to aid bioterrorists. On the one hand, the impact of the pandemic might motivate some states to use terrorist proxies in the service of biological plots, especially small-scale attacks where states want to avoid attribution or at least maintain plausible deniability. On the other hand, to the extent that COVID-19 is perceived as illustrating that a contagious agent cannot be easily contained, even when states adopt robust public health measures, it may reinforce hesitancy about launching biological attacks, especially with transmissible agents. A state sponsor of terrorism would likely recognize that providing a contagious biological weapon to a terrorist could literally or figuratively blow back and cause infections in the sponsoring state.

c) COVID-19-related public health and epidemiological measures may help reduce consequences from bioterrorism.
Public health capabilities built up in response to the pandemic might provide better defenses against bioterrorism. COVID-19 responses involved the rapid development, implementation, and refinement of public health measures aimed at containing the spread of the disease. This included requirements for mandatory stay-at-home orders, mask mandates, and rapid vaccination development and dispersal, such as the United States’ Operation Warp Speed. Such measures would also likely be useful in combating the spread of a contagious agent spread in a bioterrorist attack, and reduce the overall consequences of such an attack.

The effectiveness and applicability of public health measures will depend in large part on the contagiousness, rarity, and transmission routes of the agent chosen and the method of dissemination. If there is early warning, efforts like masking can be effective against aerosols, even of non-contagious agents like bacillus anthracis spores. However, in the absence of such warning, which is unlikely in most cases of bioterrorism, masking is generally only effective against contagious agents spread through aerosols and, to a lesser extent, against contact-mediated disease.

Likewise, viral agents that have already been well-characterized and studied may lead to rapid vaccine production and the development of treatments. Some of the breakthroughs associated with combating the coronavirus, such as mRNA-based vaccines and rapidly produced antibody treatments, will have broader application against future outbreaks of a variety of diseases. However, not all of the successes against COVID-19 are necessarily transferable to other bioagents, especially more exotic ones. The spread of uncommon or rare biological agents, viral or bacterial, in an area may delay the adoption of response measures. Public health officials may not give due consideration to a spreading disease that they are not familiar with, and so may not take measures (or may take inappropriate measures) to contain it. This dynamic is particularly acute with sophisticated biological agents—for example, more common pathogens that have been genetically modified so as to not exhibit typical behaviors.35

COVID-19 also demonstrated the existence of upper bounds on public health measure effectiveness. March 2022 Morning Consult polls show over 20 percent of Americans remain unwilling to get a COVID-19 vaccine.36 This is probably due to some combination of uncertainty about efficacy, concern over vaccine safety, distrust of public health officials, disinformation, and other factors.37 Likewise, support for policies like mask mandates and stay-at-home orders have been mixed, and states have been hesitant to reinstate those policies once dropped, even with new COVID-19 variants on the rise. While the who and why of policy opposition can be expected to shift based on normal policy fluctuations, the core concept seems applicable: Some proportion of the population will probably resist consequence-reduction measures, which does not bode well for limiting the harm of future possible bioterrorism events.

d) COVID-19 may impact threat assessment more than it impacts the threat itself.
In addition to directly affecting the threat of bioterrorism, the COVID-19 pandemic is and will impact various analysts’ assessments of bioterrorism threats, obviously including the content presented in this article. These include individuals serving in governments, whose assessments drive responses. Since to date government activity to respond to perceived bioterrorism threats vastly outweighs incidents of actual bioterrorism, it will almost certainly be the case that the pandemic affects responses to potential bioterrorism far more significantly than actual bioterrorism.w That is, heightened sensitivity to bioterrorism and related trends unconnected to COVID-19 might have a greater impact on bioterrorism risks than the COVID-19 related impacts discussed above.

Much of this depends on perceptions of how well authorities and the public have responded to the pandemic. Policymakers who believe that the response to the pandemic was adequate and effective might be lulled into a false sense of complacency regarding future biological threats, including bioterrorism, while those who perceive widespread failure on the part of governments and communities might emphasize the population’s vulnerability to disease and invest more resources in preventing the intentional spread of disease.

If the pandemic bolsters and/or undermines government responses to bioterrorism, that has implications for potential subsequent attacks as well. As Richard Danzig and his co-authors, including one of the authors of this article, noted, “Responses to a catastrophic bioterror attack are likely to greatly amplify or substantially mitigate the attack’s consequences. No less significant, if our post-attack responses fail, we are likely to encourage future attacks by demonstrating their efficacy in spreading terror.”38

The pandemic is heightening awareness of biological threats generally, of contagious pathogens more specifically, and of viral threats even more specifically. The pandemic is also sharpening knowledge about biological threats and providing a mental framework to make sense of such threats. That is, analysts and policymakers now have a far better sense of how a contagious viral pandemic might manifest and what its impacts might be, having lived through this one. In addition to being helpful, by enabling individuals to better comprehend various biological threats, it might also be counterproductive, because this particular pandemic might be a poor analogue for understanding rather different biological threats.39 COVID-19 may also create or exacerbate mirror-imaging biases in which analysts or policymakers see the harm of COVID-19, but fail to consider the ideological nuances that make such harm a demotivating factor for some bad actors.

As long as the pandemic continues—and it may continue well into the foreseeable future—it also has the potential to be a distraction from and to siphon resources away from addressing other threats, possibly to include bioterrorism threats.40 These effects might cast a long shadow into the future because lessened counterterrorism efforts now may manifest in plots at a later time. Of course, such distractions and siphoning can only occur insofar as bioterrorism response and general bio-preparedness are distinct. And whether such a trade-off is justified necessarily depends on comparing actual harm (COVID-19) versus the theoretical harm of a hypothetical bioterrorism attack.

The massive economic and human toll of COVID-19 illustrates the potential consequences of a major, contagious bioterrorism attack. But the reality is that COVID-19 probably has not changed the bioterrorism threat landscape all that much. Table 2 indicates the portions of the Bioterrorism Classification Schema that are likely to be affected by COVID-19. Most changes are moderate, with at most an increase or decrease by one quantity from pre-COVID values. Moreover, with respect to the Agents portion of the Schema, only contagious agents are affected. Terrorist ideology and related motivations concerning biological weapons are a key discriminating factor. Overall, the types of terrorists most likely to pursue biological weapons have not changed appreciably from before the COVID-19 pandemic. The only increases were seen in the case of apocalyptic/millenarian groups, environmental extremists, and extreme right-wing groups with maximalist (e.g., accelerationist) ideologies. Several of the other types of terrorist ideologies either decreased or remained the same (since they were already at the lowest level). Islamist extremists in general are estimated to have decreased their interest in contagious agents across the board, except for the subset that is less concerned with inflicting damage on their co-religionists.

Moving from motivation to capability, the more widespread research activity and laboratories dealing with sophisticated viral pathogens might provide increased opportunities for scientist insiders to access these agents or to prepare agents for aerosol dispersal. It might also provide more opportunities for small terrorist cells to steal such agents. In addition, the diffusion across the globe of many sophisticated biotechnologies relevant to working with viruses might provide state sponsors of terrorism with capabilities to produce sophisticated bioagents that they can bequeath to their terrorist proxies. Although arrived at via a somewhat different analytical approach, the results here accord closely with those reached by Gregory Koblentz and Stevie Kiesel in a recent study.41

When looking beyond the threat to efforts to counter it, the authors’ analysis indicates that the public health efforts created to reduce COVID-19 harm may be applicable to bioterrorism, but only if either warning systems provide reliable early alerts or the agent used is contagious. On a meta-level, COVID-19 may influence analyst risk assessment more than the threat actually changes, through greater awareness of biological threats, personal assessments of COVID-19 response, and mirror-imaging biases.

What should governments do about all this? First, government agencies interested in countering bioterrorism should prioritize groups holding apocalyptic ideologies, whether these take the form of standalone cults or the fringes of other extremist movements like Islamist extremists or radical environmentalists. These are the groups for whom COVID-19 has likely bolstered interest in bioterrorism most. Domestic intelligence agencies should identify and monitor these groups and look for indicators of interest in biological terrorism.42 Particularly noteworthy is whether these groups seek to acquire specialized biological laboratory equipment, find employment for their members in biotechnology-related facilities, or recruit individuals with expertise in the biological sciences.

Second, intelligence collection and analysis efforts should focus on areas of new vaccine and other biotechnological development, including drug delivery technologies. Those are areas where extremists may seek to acquire capability or individuals who become radicalized can do particular harm. Of particular interest should be known terrorist groups showing an interest in vaccine-related activities to potentially use that knowledge in support of bioterrorism or state sponsors of terrorism whose biological weapons capabilities show signs of growing. State-sponsored groups that control territory and support civilian populations may create false positives, however, because some of those groups who control territory may have a legitimate interest in vaccine related activities as part of their provision of social services. Of course, such behavior may also be a mask for biological weapons-related activities, but this is far less likely for groups whose ideologies display lower interest in bioterrorism in the Bioterrorism Classification Schema, such as ethno-nationalist and extreme far-left groups.

Third, at the level of national strategy, emphasis should be placed on early warning, preparedness, and response to biological agents writ large, as opposed to a particular focus on bioterrorism. Response to a terrorist-induced outbreak of a contagious disease is likely to be much the same as any other disease, requiring an emphasis on managing hospital and healthcare resources, acquiring and distributing protective gear, and minimizing person-to-person interaction. Nonetheless, some specific differences that apply to both biological warfare and bioterrorism warrant attention. Potential bioterrorists (or covert state operatives) may utilize biological agents that are uncommon to a particular locality or nation. In that scenario, health officials will be less if not entirely unprepared to recognize the symptoms, adopt appropriate risk reduction policies, and engage in general response. While unlikely due to the sophistication required, bioterrorists may also genetically modify biological agents to increase survivability, lethality, or transmissibility. This would complicate public health response, potentially causing the agent to spread in unexpected ways.

COVID-19 might have reinforced fears of catastrophic bioterrorism, but the complex motivational and capability-related dynamics surrounding the phenomenon reveal that the strategic nature of the threat has not appreciably changed since before the pandemic. This is not to say, however, that bioterrorism is not or will not be a substantial threat; the preliminary assignment of values to the Bioterrorism Classification Schema suggests there are several areas where the threat might be high or growing. What the authors are arguing is that despite superficial expectations that COVID-19 would impact bioterrorism as much as it has impacted many other areas of society, upon closer examination the pandemic appears unlikely to affect the bioterrorist threat emanating from the vast majority of terrorist groups.     CTC

Gary A. Ackerman is an Associate Professor and Associate Dean for Research in the College of Emergency Preparedness, Homeland Security and Cybersecurity at the University at Albany (SUNY), where his research focuses on assessing emerging threats and understanding how terrorists and other adversaries make tactical, operational, and strategic decisions, particularly regarding innovating in their use of weapons and tactics.

Zachary Kallenborn is a Policy Fellow at the Schar School of Policy and Government, a Research Affiliate with the Unconventional Weapons and Technology Division of the National Consortium for the Study of Terrorism and Responses to Terrorism (START), an officially proclaimed U.S. Army “Mad Scientist,” and Senior Consultant at ABS Group. His research on autonomous weapons, drone swarms, weapons of mass destruction (WMD), and WMD terrorism has been published widely.

Philipp C. Bleek is Associate Professor of Nonproliferation and Terrorism Studies, Fellow at both the James Martin Center for Nonproliferation Studies and Center on Terrorism, Extremism, and Counterterrorism, and Coordinator at the Cyber Collaborative, all at the Middlebury Institute of International Studies at Monterey. He works on the causes, consequences, and amelioration of chemical, biological, radiological, and nuclear weapons threats from both state and non-state actors at the intersection of academia, non-governmental organizations, and government.

© 2022 Gary Ackerman, Zachary Kallenborn, Philipp Bleek


Substantive Notes
[a] This article uses the same definition of terrorism as the Global Terrorism Database: “the threatened or actual use of illegal force and violence by a non-state actor to attain a political, economic, religious, or social goal through fear, coercion, or intimidation.” Gary LaFree and Laura Dugan, “Introducing the Global Terrorism Database,” Terrorism and Political Violence 19:2 (2007): pp. 181-204.

[b] While they are both involved in the classification of phenomena, the key differentiating factor is that taxonomies are empirical and inductive (i.e., constructed based on observations of the world), whereas typologies are conceptual and deductive, with a structure imposed by the designer. The effort here therefore includes elements of both classification approaches. See Kevin B. Smith, “Typologies, taxonomies, and the benefits of policy classification,” Policy Studies Journal 30:3 (2002); Susan Lambert, “Do We Need a ‘Real’ Taxonomy of e-Business Models?” School of Commerce Research Paper Series 6:6 (2005).

[c] It should be noted that the Global Terrorism Database only covers actual terrorist attacks and attempted attacks, whereas the POICN database includes other activities as well, such as plots, attempts to acquire biological agents, weaponization of agents, and so forth.

[d] For example, Thomas Guarrieri and Collin Meisel found that individuals oriented around a single issue were more likely to pursue chemical and biological weapons than those who were extreme far-left or extreme far-right in orientation, while McCann found that religiously motivated (especially Islamist) terrorist groups were significantly more likely to pursue biological weapons. Thomas R. Guarrieri and Collin J. Meisel, “Extremists and Unconventional Weapons: Examining the Pursuit of Chemical and Biological Agents,” Behavioral Sciences of Terrorism and Political Aggression (2019); Wesley S. McCann, “Outbreak: A Comprehensive Analysis of Biological Terrorism,” Studies in Conflict & Terrorism (2022).

[e] For example, Jean Pascal Zanders maintains that a higher-end bioagent production capability is far easier for a “vertically organized, highly integrated and ideologically uniform” group than one that is amorphous or based on small cells. Jean Pascal Zanders, “Assessing the Risk of Chemical and Biological Weapons Proliferation to Terrorists,” Nonproliferation Review 6:4 (1999): p. 30.

[f] There are extensive ideological and operational links between the extremist animal rights and environmentalist communities. See Zachary Kallenborn and Philipp C. Bleek, “Avatars of the Earth: Radical Environmentalism and Chemical, Biological, Radiological, and Nuclear (CBRN) Weapons,” Studies in Conflict & Terrorism 43:5 (2020) and Gary Ackerman, “Beyond Arson? A Threat Assessment of the Earth Liberation Front,” Terrorism and Political Violence 15:4 (2004).

[g] This does not prevent new categories from being added if it becomes necessary based on new empirical evidence.

[h] In the event that it is known that a terrorist group (either small homegrown cell, formal, or state-sponsored) possesses such an insider, then for practical risk assessment purposes, an analyst would utilize the maximum of the insider capability score and the capability score for the type of terrorist group for each agent and delivery method. See Illustrative Example 2 in the appendix.

[i] The main steps involved in developing a bioweapon consist of: a) acquiring a seed stock of the agent; b) culturing the agent to increase the amount; c) refining and preparing the agent to make it suitable for storage, transportation, and delivery (e.g., drying, milling); and d) mating it with a mechanism for dissemination. Gary A. Ackerman and Kevin S. Moran, “Bioterrorism and Threat Assessment,” Paper #22 commissioned by the Weapons of Mass Destruction Commission (The “Blix” Commission), 2004. In this CTC Sentinel article, the authors treat all of the steps that require biological expertise (a through d) in a single component.

[j] Survivability usually refers to the ability of a bioweapons agent to persist in the environment without being rendered harmless by such factors as sunlight, oxidation, and atmospheric forces.

[k] The field of synthetic biology is concerned with designing and building new biological materials (e.g., enzymes, proteins, lipids not already found in nature), devices, systems, and/or functions, especially by (re)programming DNA circuits to manipulate cellular behavior. Gary A. Ackerman and Lauren E. Pinson, “An Army of One: Assessing CBRN Pursuit and Use by Lone Wolves and Autonomous Cells,” Terrorism and Political Violence 26:1 (2014): footnote 3.

[l] The Aerosol/Spray category involves dissemination that after initial release allows natural air currents and gravity to disperse the particles or droplets, whereas the Explosive category involves mechanisms that use the kinetic energy of a detonation to disperse particles that are also technically aerosols.

[m] In this context, “Latent” follows the description of the POICN Database as a delivery system where an agent “is left out without forcing direct contact. For instance, leaving breakable vials of an agent on the floor intending for the target to step on the vials and release the agent.” “POICN Database Codebook V8.71,” December 2017.

[n] This would require, for instance, robust analyses of databases like POICN and the Chemical and Biological Non-state Adversaries Database (CABNSAD), while taking into account the current strategic orientation and capabilities of prominent adversaries in each category, as well as recent technological developments that might affect these. This can be done, but would take considerable resources, as demonstrated in other bioterrorism-related risk assessments, such as the Bioterrorism Risk Assessment, National Research Council, 2008, and U.S. Department of Homeland Security, Bioterrorism Risk Assessment: A Call for Change (Washington, D.C.: National Academies Press, 2008).

[o] The matrix as presented does not capture possible interaction effects between its components, which would need to be considered if the BTCS were to be utilized as a basis for assessing threat. For example, in some cases, motivation can drive capability, or vice versa, while there might be dependencies between certain agents and delivery mechanisms that are difficult to represent in a simple two-dimensional matrix. The authors leave such enhancements to future research.

[p] Islamist extremist groups also tend to be particularly good fits for the criteria for pursuing CBRN terrorism (being embedded in alliance structures, being based in an authoritarian state with relatively strong connections to a globalized world, being relatively large, and having more experience with terrorism in general) derived in Victor H. Asal, Gary A. Ackerman, and R. Karl Rethemeyer, “Connections Can Be Toxic: Terrorist Organizational Factors and the Pursuit of CBRN Weapons,” Studies in Conflict & Terrorism 35:3 (2012).

[q] This assertion does not include the “idiosyncratic” category, which is discussed in Box 1.

[r] Markus Binder and one of the authors (Gary Ackerman) analyzing the POICN database observe that toxins were the primary agent in most of the cases in the database (which, as noted earlier, include failed, aborted, and thwarted plots). Out of the 86 bio-incidents where the nature of the agent could be identified, 53 of these (61.6 percent) were toxins, with the dominant (67.9 percent) toxin being ricin, which featured in 36 events. Markus K. Binder and Gary A. Ackerman, “Pick Your POICN: Introducing the Profiles of Incidents involving CBRN and Non-state Actors (POICN) Database,” Studies in Conflict and Terrorism 44:9 (2021). Frida Ekren provides a more recent example where, in 2019, a cell of the Islamic State-linked Indonesian group Jamaah Ansharut Daulah plotted to disperse the toxin abrin by explosive as part of a suicide bombing. Frida Ekren, “Understanding the Current Threat of Bioterrorism: A study of Violent Non-State Actors’ Online Instruction Manuals,” master’s thesis, Charles University, July 2021.

[s] Among others, in the 1980s the extreme far-right apocalyptic group the Covenant, Sword and the Arm of the Lord in the United States plotted to attack the water supplies of major cities with the chemical agent cyanide, which provides some indication of possible proclivities for disseminating bioagents through this mechanism. See Kerry Noble, Tabernacle of Hate: Seduction into Right-Wing Extremism, 2nd ed. (Syracuse, NY: Syracuse University Press, 2010).

[t] Thirty-one percent of events in the POICN database where a lone actor pursued a biological weapon resulted in actual attacks with agent dispersal, while only 19 percent of similar events involving formal organizations reached this level. Ackerman and Pinson.

[u] As an example of such thinking among this milieu, there is the following appeal by an environmentalist writing under the pseudonym of “Gula”: “Contributions are urgently solicited for scientific research on a species-specific virus that will eliminate Homo shiticus from the planet.” Gula, “Eco-Kamikazes Wanted,” Earth First! Journal (1989): p. 21.

[v] There is a subsection of the Islamist extremist milieu that has a more pronounced apocalyptic orientation, as well as those who have justified extensive “collateral damage” among Muslims in the service of their jihad. For example, there is the widely referenced fatwa of Nasir al-Fahd’s that permitted the killing of millions with unconventional weapons as well as the targeting of areas including many Muslim residents. Nasir bin Hamad al-Fahd, “A Treatise on the Legal Status of Using Weapons of Mass Destruction Against Infidels,” Rabi` I 1424 (May 2003). Al-Qa`ida ideologue Anwar al-Awlaki also permitted the use of poisons and other WMD in densely populated areas. Anwar al-Awlaki, “Targeting the Populations of Countries that are at War with the Muslims,” Inspire 8 (2011).

[w] There is a lively debate among analysts about the severity of the bioterrorism threat and the responses it warrants. For a particularly skeptical perspective on the threat, see Milton Leitenberg, “The Self-Fulfilling Prophecy of Bioterrorism,” Nonproliferation Review 16:1 (2009): pp. 95-109.

[1] Andrea Shalal, “IMF Sees Cost of COVID Pandemic Rising Beyond $12.5 Trillion Estimate,” Reuters, January 20, 2022.

[2] Paul D. Shinkman, “Navy to Evacuate USS Theodore Roosevelt Amid Coronavirus Pandemic,” U.S. News & World Reports, April 1, 2020.

[3] Adrienne Mayor, Greek Fire, Poison Arrows, & Scorpion Bombs: Biological and Chemical Warfare in the Ancient World (New York: Abrams Press, 2003).

[4] For more detailed treatments of different aspects of bioterrorism, see Jonathan B. Tucker ed., Toxic Terror: Assessing the Terrorist Use of Chemical and Biological Weapons (Cambridge, MA: MIT Press, 2001); Raymond A. Zilinskas and Rebecca Katz eds., Encyclopedia of Bioterrorism Defense (New York: Wiley, 2011); Gregory Koblentz, Living Weapons: Biological Warfare and International Security (Ithaca, NY: Cornell University Press, 2011); and Wesley S. McCann, “Outbreak: A Comprehensive Analysis of Biological Terrorism,” Studies in Conflict & Terrorism (2022).

[5] “Global Terrorism Database (GTD),” START (National Consortium for the Study of Terrorism and Responses to Terrorism), University of Maryland, 2021.

[6] Markus K. Binder and Gary A. Ackerman, “Pick Your POICN: Introducing the Profiles of Incidents involving CBRN and Non-state Actors (POICN) Database,” Studies in Conflict and Terrorism 44:9 (2021).

[7] Binder and Ackerman.

[8] Gary Ackerman and Markus Binder, Chemical and Biological Non-State Adversaries Database (CABNSAD) (College Park, MD: START, 2017).

[9] Markus Binder, Gary Ackerman, Cory Davenport, Herbert Tinsley, Rebecca Earnhardt, Crystal Watson, Matt Watson, and Tara Kirk Sell, “Profiling the CB Adversary: Motivation, Psychology and Decision,” START, September 2017, using data drawn from the CABNSAD database.

[10] Kalicharan Veera Singam and Kyler Ong, “State Sponsored Terrorism During the COVID-19 Pandemic,” Counter Terrorist Trends and Analyses 13:3 (2021).

[11] “Bioterrorism Agents/Diseases,” Centers for Disease Control and Prevention.

[12] Gary A. Ackerman and Kevin S. Moran, “Bioterrorism and Threat Assessment,” Paper #22 commissioned by the Weapons of Mass Destruction Commission (The “Blix” Commission), 2004.

[13] Gigi Gronvall, “The Security Implications of Synthetic Biology,” Survival 60:4 (2018): pp. 165-180; Claire Marris, Catherine Jefferson, and Filippa Lentzos, “Negotiating the dynamics of uncomfortable knowledge: The case of dual use and synthetic biology,” BioSocieties 9:4 (2014); Diane DiEuliis, Charles D. Lutes, and James Giordano, “Biodata Risks and Synthetic Biology: A Critical Juncture,” Journal of Bioterrorism and Biodefense 9 (2018): pp. 1-12; Gregory D. Koblentz, “The De Novo Synthesis of Horsepox Virus: Implications for Biosecurity and Recommendations for Preventing the Reemergence of Smallpox,” Health Security 15 (2017): pp. 620-628; Omar Akbari Omar et al., “Safeguarding gene drive experiments in the laboratory,” Science 349:6,251 (2015): pp. 927-929.

[14] Pan Tao, Jingen Zhu, Marthandan Mahalingam, Himanshu Batra, and Venigalla B. Rao, “Bacteriophage T4 Nanoparticles for Vaccine Delivery Against Infectious Diseases,” Advanced Drug Delivery Review (2018): pp. 1-16.

[15] Zachary Kallenborn and Philipp C. Bleek, “Swarming destruction: drone swarms and chemical, biological, radiological, and nuclear weapons,” Nonproliferation Review 25:5-6 (2018): pp. 523-543.

[16] Ackerman and Moran.

[17] Seth Carus, “The Rajneeshees (1984),” in Jonathan B. Tucker ed., Toxic Terror: Assessing Terrorist Use of Chemical and Biological Weapons (Cambridge, MA: MIT Press, 2001).

[18] Gary Ackerman, “CBRN Terrorism,” in Andrew Silke ed., Routledge Handbook of Terrorism and Counter-Terrorism (New York: Routledge, 2019).

[19] McCann; Gary A. Ackerman, Jeffrey M. Bale, Victor Asal, R. Karl Rethemeyer, Amanda Murdie, Mila Johns, and Markus K. Binder, Anatomizing Chemical and Biological Non-State Adversaries: Identifying the Adversary, report prepared for the Project on Advanced Systems and Concepts for Countering WMD (PASCC), Center on Contemporary Conflict, Naval Postgraduate School, under Grant No. N00244-12-1-0033 (College Park, MD: National Consortium for the Study of Terrorism and Responses to Terrorism, 2014).

[20] Ackerman, Bale, Asal, Rethemeyer, Murdie, Johns, and Binder.

[21] Zachary Kallenborn and Philipp C. Bleek, “Avatars of the Earth: Radical Environmentalism and Chemical, Biological, Radiological, and Nuclear (CBRN) Weapons,” Studies in Conflict & Terrorism 43:5 (2020): pp. 351-381; Gary Ackerman, “Beyond Arson? A Threat Assessment of the Earth Liberation Front,” Terrorism and Political Violence 15:4 (2004): pp. 143-170.

[22] Frida Ekren, “Understanding the Current Threat of Bioterrorism: A study of Violent Non-State Actors’ Online Instruction Manuals,” master’s thesis, Charles University, July 2021.

[23] Gary Ackerman and Michelle Jacome, “WMD Terrorism: The Once and Future Threat,” PRISM: The Journal of Complex Operations 7:3 (2018).

[24] Daniel Byman, “Iran, Terrorism, and Weapons of Mass Destruction,” Studies in Conflict & Terrorism 31:3 (2008): pp. 169-181.

[25] Ackerman and Jacome.

[26] Seth Carus and Raymond Zilinskas, Possible Terrorist Use of Modern Biotechnology Techniques (Washington, D.C.: National Defense University Center for Counterproliferation Research, 2002); Stephen Hummel, F. John Burpo, Jeremy Hershfield, Andrew Kick, Kevin J. O’Donovan, and Jason Barnhill, “A New Age of Bioterror: Anticipating Exploitation of Tunable Viral Agents,” CTC Sentinel 14:4 (2022).

[27] Gregory D. Koblentz and Stevie Kiesel, “The COVID-19 Pandemic: Catalyst or Complication for Bioterrorism?” Studies in Conflict & Terrorism (2021).

[28] Seth Carus, “R.I.S.E.” in Toxic Terror.

[29] Gary Ackerman and Hayley Peterson, “Terrorism and COVID-19: Actual and Potential Impacts,” Perspectives on Terrorism 14 (2020): pp. 59-73; “Twenty-ninth report of the Analytical Support and Sanctions Monitoring Team submitted pursuant to resolution 2368 (2017) concerning ISIL (Da’esh), Al-Qaida and associated individuals and entities,” United Nations Security Council, February 3, 2022.

[30] Ackerman and Peterson.

[31] Ibid.

[32] Ibid.

[33] Ibid.; Filippa Lentzos, Gregory D. Koblentz, and Joseph Rodgers, “The Urgent Need for an Overhaul of Global Biorisk Management” CTC Sentinel 15:4 (2022).

[34] Lentzos, Koblentz, and Rodgers; Jean-Louise Excler, Melanie Saville, Seth Berkley, and Jerome H. Kim, “Vaccine development for emerging infectious diseases,” Nature Medicine 27 (2021): pp. 591-600; “WHO works to spread COVID vaccine technology to more nations,” Associated Press, February 23, 2022; Stephanie Nolen, “Here’s Why Developing Countries Can Make mRNA Covid Vaccines,” New York Times, October 22, 2021.

[35] Hummel, Burpo, Hershfield, Kick, O’Donovan, and Barnhill.

[36] “The U.S. Vaccine Dashboard,” Morning Consult, updated March 17, 2022.

[37] Cary Funk and John Gramlich, “10 Facts about Americans and Coronavirus Vaccines,” Pew Research, September 20, 2021.

[38] Richard Danzig, Rachel Kleinfeld, and Philipp Bleek, “After an Attack: Preparing Citizens for Bioterrorism,” Center for a New American Security, June 1, 2007.

[39] Only somewhat relatedly, on analogies and policy decisions about war and peace, see Yuen Foong Khong, Korea, Munich, Dien Bien Phu, and the Vietnam Decisions of 1965 (Princeton, NJ: Princeton University Press, 1992).

[40] Ackerman and Peterson.

[41] Koblentz and Kiesel.

[42] For a list of such indicators, see Ackerman et al. (2017).

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