Phase II safety and immunogenicity study of type F botulinum toxoid in adult volunteers

Abstract An aluminum hydroxide ( alum )-adsorbed, purified, botulinum F toxoid (Bot F) vaccine was manufactured to be administered as a stand-alone monovalent vaccine or to be added to the current botulinum pentavalent toxoid vaccine to make a hexavalent vaccine. We conducted a phase II trial of the Bot F vaccine over 3 years in 144 healthy adult volunteers to identify one of three vaccination schedules that was safe and maximally immunogenic for adult volunteers. We vaccinated 116 volunteers 1–3 times with Bot vaccine, and 28 volunteers 1–3 times with a licensed, alum-adsorbed hepatitis B vaccine (Engerix-B) as a reaction control group. After 1 year, 42 Bot volunteers with low, mouse anti-toxin titers ( 0.02 IU/ml) than did vaccinations given over 28 days (days 0, 7 and 28). Vaccine reactogenicity and immunogenicity were similar over 42 days whether administered subcutaneously or intramuscularly. However, even the most immunogenic schedule left 7–16% of volunteers unprotected at day 56 and 33–42% of vaccinees unprotected at 1 year. The booster dose administered at 1 year induced high levels of protective serum anti-toxin in all persons assayed which persisted for at least one additional year. A more potent vaccine formulation will be required to protect more individuals after primary immunization.