The state is encouraging more than 80 people to take antibiotics and anthrax vaccine after an environmental sample at the United Campus Ministry in Durham tested positive for anthrax.
The announcement today comes after a young woman remains in critical condition with gastrointestinal anthrax. She attended a drum circle at the ministry building, which the state ordered closed until further notice.
However, many questions remain about the vaccine's efficacy and safety. Whether vaccination is appropriate in the current setting is another question, since anthrax vaccine has not been FDA-approved for this purpose, and provided no additional benefit for persons who took antibiotics after anthrax exposure in 2001. When CDC offered the vaccine for post-exposure prophylaxis in 2001, it failed to make a positive recommendation for the vaccine's use, since no data supported a presumption of benefit from the vaccine then, and none support it now. In fact, the New Hampshire department of health rightly points out that, "The vaccine is not effective in prevention of the disease after someone has been exposed." Although CDC's Advisory Committee on Immunization Practices recently voted in favor of post-exposure anthrax vaccination, the recommendation is provisional and has not been approved by CDC's director or DHHS.
Weeks (or months) after an exposure, one's risk of developing anthrax drops toward zero. The likelihood of another case developing in New Hampshire is extraordinarily low.
If anthrax vaccine was perfectly safe, people who might have been exposed to anthrax would do well to use it as extra insurance against the disease. But there are troubling safety questions. The GAO (the investigative arm of Congress) reported in 2007 that, "Officials from the VHC Network and CDC estimate that between 1 and 2 percent of immunized individuals may experience severe adverse events, which could result in disability or death." I discussed this earlier here.
Below is a table from the largest trial of Biothrax anthrax vaccine conducted in humans, by CDC, published in the October 1, 2008 Journal of the American Medical Association. A total of 1564 people were entered in the study, and 1300 received anthrax vaccine. In the 1564 subjects, 229 serious adverse events occurred during the 43 month trial. A listing of all the adverse events, comparing the vaccine and placebo groups, has yet to be published--but study authors reported that the following 7 serious adverse events (including two people with new breast cancers) were possibly related to the vaccine:
Table 7. Serious Adverse Events Rated as Possibly Associated With the Study Agent (anthrax vaccine) Since Study Initiation
A Latin phrase encapsulates the anthrax vaccination issue, for those civilians in a position to choose whether to take it: Caveat Emptor (or in English, Let the Buyer Beware).