Vaccine: A pentavalent toxoid of C. botulinum toxin types A, B, C, D, and E is available as an IND for preexposure prophylaxis. It will likely remain under IND status as efficacy testing in humans is not feasible. This product has been administered to several thousand volunteers and occupationally at-risk workers, and historically induced serum antitoxin levels that correspond to protective levels in experimental animals. At-risk laboratory workers remain the primary recipients. The currently recommended primary series of 0, 2, and 12 weeks, followed by a 1 year booster induces protective antibody levels in > 90 percent of vaccinees after 1 year. Adequate antibody levels are transiently induced after three injections, but decline before the 1-year booster. Previously, additional need for boosters was determined by antibody testing. Since 2001, the potency of the vaccine appears to be declining. In fact, in 2004 the vaccine failed potency tests for B, C, D, and E serotypes. In the future, changes may be made to the protocol, to add a dose at 6 months and to add annual booster doses. Laboratory workers should be aware that the vaccine cannot be used as the sole protection against a possible laboratory exposure to A-E serotypes.

Contraindications to the vaccine include sensitivities to alum, formaldehyde, and thimerosal, or hypersensitivity to a previous dose. Reactogenicity is mild, with 2 to 4 percent of vaccinees in a passive surveillance system reporting erythema, edema, or induration at the local site of injection which peaks at 24 to 48 hours. The frequency of such local reactions increases with subsequent inoculations; after the second and third doses, 7 to 10 percent will have local reactions, with higher incidence (up to 20 percent or so) after boosters. Severe local reactions are rare, consisting of more extensive edema or induration. Systemic reactions are reported in up to 3 percent, consisting of fever, malaise, headache, and myalgia. Incapacitating reactions (local or systemic) are uncommon. More recent data based on active surveillance revealed 23 percent reported local reactions and 7.4 percent reported systemic reactions. The vaccine should be stored at 2-8OC (not frozen).

The vaccine is typically recommended for selected individuals or groups who work with the botulinum toxins in the laboratory. Because of the challenges of administering an IND product in an operational environment, and due to the concerns related to vaccine potency, only those individuals who have an extremely high risk of exposure to botulinum toxins in the field should be considered for receipt of the vaccine. There is no indication at present for using botulinum antitoxin as a prophylactic modality except under extremely specialized circumstances.

Posteposure prophylaxis, using the heptavalent antitoxin, has been demonstrated effective in animal studies; however, human data are not available, so it is not recommended for this indication. The antitoxin should be considered for this purpose only in extraordinary circumstances.

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