Utility of Anthrax vaccines in a Bioterrorism Attack

Utility of Anthrax Vaccines in a Bioterrorism Attack

 

Author: Manisha Samy

 

Another potential countermeasure to an anthrax bioterrorism attack, one not considered by the Bravata et al study, is vaccination. This may include pre-vaccination before exposure and the possibility of post-exposure vaccination. According to an anthrax countermeasure review, the optimal post-exposure treatment of “immunologically naïve indiviuals should include a combination of vaccination plus antibiotic therapy” (Klinman). This raises questions regarding the cost-effectiveness of providing both measures, especially considering that the probability of another anthrax bioterrorism attack is unknown. A combination post-therapy strategy will require additional pharmaceuticals to be stored in local and state inventories, and yet again policy issues arise as to whom should receive treatment first given that not a 100% of a population can receive proper treatment. A question that may arise is why are antibiotics the current treatment of choice given that the population can be pre-vaccinated?

            Anthrax Vaccine Adsorbed (AVA), although a licensed vaccine in the US, has concerns over safety and immunogenicity (Klinman). Second generation vaccines based on purified recombinant protective antigen are still in clinical trials; however, magnitude and duration of resultant protective response is modest at best (Klinman). Third generation anthrax vaccines hope to include a variety of immunization platforms, antigens, adjuvants, and delivery methods (Klinman). AVA has never been tested for efficacy in inhalation anthrax, but was shown to reduce incidence of cutaneous anthrax in wool workers (Klinman).

As discussed before, there are three forms of anthrax disease depending on route of infection. The Bravata et al study provides the optimal stockpiling and treatment decisions based on antibiotic treatment based on an aerosol anthrax attack, thus referring to inhalation anthrax in infected persons. Because AVA has never been tested in human inhalation anthrax incidents, creating an effective and cost-effective treatment and stockpiling policy becomes all the more complex. Though, animal models including non-primates have, in fact,  proven AVA to be efficacious in combating aerosol exposure to anthrax (Klinman). We are in the era of great advances in biotechnology and solutions, so why is the development of vaccination against anthrax so slow—especially considering that the first vaccine for animals infected with anthrax was developed in 1880? The slow procession towards an effective vaccination for humans can be explained through bioethics.

AVA has been tested in cutaneous anthrax in humans because there are enough naturally occurring incidents of it to test its effectiveness. Naturally occurring aerosol incidents of anthrax is not possible in terms of the level of spores one must be exposed to in order to contract inhalation anthrax. The only way to test how effective AVA is in human inhalation anthrax would be to deliberately expose humans to enough B. anthracis spores. Human testing is unethical and dangerous. Thus the only way to test AVA effectiveness in humans who would have been infected with inhalation anthrax would be to wait for another anthrax bioterror attack on indviduals who have already received the vaccine. Until then, the best case scenario is to test on animals or wait for the advent of a better testing mechanism without human trial experiments.

An adequate vaccine countermeasure can prove to be one of the best treatment and preparedness plan. An adequate vaccine may provide the necessary effectiveness to allow the “antimicrobial course to be shortened from the recommended 60 days to as few as 14 days” (Wright). The significance in this lies in the conclusion made in both the Bravata et al and Houck et al study: Mortality rates are directly correlated with treatment adherence rates, thus the shorter the treatment period, the greater the likelihood is that a given individual will adhere to treatment to its completion. Vaccines have the ability to reduce treatment to just 23.3% of the current treatment time! Furthermore, it may prove to be more cost-effective from a societal perspective with less capital being spent on other countermeasures, labor required in maintain treatment facilities to treat all individuals, lower mortality rates, less shipments of the current 3-dose antibiotic treatment, etc.

Perhaps rather than focusing on just strategic deployment of antibiotics, we should spend more capital and time on anthrax vaccine research and creating greater incentives for pharmaceuticals companies to invest time in this research. This may also require changes in current FDA protocols in approving experimental trials.

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Klinman, Dennis M., Masaki Yamamoto, Debra Tross, and Koji Tomaru. "Anthrax Prevention and Treatment: Utility of Therapy Combining Antibiotic plus Vaccine."Expert Opinion on Biological Therapy (2009): 091016103243051. Print.

Wright, Jennifer G., and Conrad P. Quinn. "Use of Anthrax Vaccine in the United States Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009." Morbidity and Mortality Weekly Report 59.RR-6 (2009): n. pag. Print.