Venom immunization: IgG/IgE titers, safety, risk, and methods of the VIPRBITEM cohort.

Background: This is the first study to examine a cohort that engages in the practice of immunization with snake venoms. In this practice, either fresh wet venom or venom reconstituted from freeze-dried form is used in vaccination protocols to produce hyper-immunity to venom.

Methods: This is a retrospective community-initiated collaborative research (CICR) project that collated the records of venom immunization. Records of schedules, formulations, photographs, medical records, and diaries were collated from existing practitioners and evaluated by inspection and interviews. One accidental bite was observed over 3 days, with vital signs, and photographic records of swelling taken to verify reality of the bite. Over 74 snake-genera man-years, and 24 man-years of injection data from 8 participants, for 22 species of venomous snakes from Elapidae and Viperidae are represented. Six of those participants had detailed records of date, dose and effects.

Results: IgG titers to 6 venoms for 4 cohort members tested of 8 included 2 with clear hyper-immune status. IgE titers were elevated for some. In 861 injections, records showed a rate of atopy/anaphylaxis of 4.3%, an infection rate of 0.58% and an abscess rate of 1.51% . Serious adverse reactions were rare and these appeared to be linked to overly aggressive immunization schedules and formulation accidents. We note that greater cross-immunity of IgE over IgG is suggested. Two basic protocols were followed, one was an approximate one month interval, the other was one or more injection(s) per week. In 176 envenomations, 175 were without antivenom treatment, two hospitalizations occurred, and one received full antivenom treatment. Dry bites were not included in our dataset. Envenomations showed a 1.14% rate of atopy/anaphylaxis, a 0.57% rate of infection and a 1.7% rate of abscess.

Conclusions: Immunization of humans to snakebite is effective, and reasonably safe with care. Injection records suggest immune cross-reactivity between ophidians within the same family, and better cross-reactivity within the same genera. A cohort participant was pronounced dead based on EEG, and then recovered without treatment. A neurotoxin case with "brain death" EEG should stay on life support for 6 weeks to allow time for the immune system to clear venom.