Anthrax vaccines for human use were first tested in the 1950s. Six hundred scientists were administered the vaccine at Fort Detrick, and the vaccine was declared safe for human use. After the initial testing, field studies were conducted on the vaccine’s safety and effectiveness among workers in industrial settings who were known to be at high risk for anthrax. This vaccine was supplied by Wright and Associates of the U.S. Army Chemical Corps of Fort Detrick.
Between 1950 and 1959, workers at four mills in the U.S. Northeast were allowed to participate in the study. Those who received the experimental vaccine were administered a product containing a modified version of the Vollum strain of B. anthracis, which included 0.1 percent aluminum potassium sulfate (alum). The control group received a “placebo” containing 0.1 percent alum. Participants were administered a primary vaccine series of 3 doses given at 2-week intervals and three additional booster doses beginning at six months given at 6-month intervals.
During the study period, 26 cases of anthrax were reported, with four occurring in persons who were partially vaccinated and one in a person who was fully vaccinated.
The trial participants were examined 24 and 48 hours after each vaccine dose for local or systemic reaction symptoms. Swelling, redness, and itching at the injection site were the most common symptoms reported after vaccination, with most symptoms resolving within two days. However, some vaccine recipients developed persistent nodules at the injection site, and others reported significant swelling. Most reactions occurred after the second and sixth vaccine dose. There were also reports of reactions among persons who received the aluminum-containing “placebo”; however, the symptoms were considered less severe than those who received the vaccine. Thirty-five percent of vaccine recipients reported localized adverse events following vaccination.
Researchers reported that only two systemic reactions occurred among study participants, and these individuals also experienced injection site swelling. Both individuals reported malaise lasting about 24 hours after vaccination. Two study participants who were previously diagnosed with cutaneous anthrax were inadvertently administered the vaccine, and both experienced severe localized reactions, including swelling, redness, and itching. Neither individual received any additional vaccine doses. One person who had previously recovered from inhalation anthrax was administered at least one anthrax vaccine dose but did not report any side effects.
Researchers reported that while the vaccine appeared to be protective against cutaneous anthrax, the data was inconclusive on whether protection would extend to inhalation anthrax. Additionally, they reported that the vaccine did not offer long-term protection, and three primary vaccine doses and a booster dose were needed to ensure protection against anthrax for at least six months. The vaccine was declared safe and effective based on this study published in 1962, which involved only 1,249 individuals.
This early vaccine was initially manufactured by Merck Sharp & Dohme; however, the vaccine’s original license was granted to the Michigan Department of Public Health by the Division of Biologics of the National Institutes of Health because the FDA had not yet been established.
