Duration of protection following vaccination Vaccination usually prevents smallpox infection for at least ten years. If symptoms appear, they are milder and mortality is less in vaccinated than in nonvaccinated persons. Even when immunity has waned, vaccinated persons shed less virus and are less likely to transmit the disease. Complications of vaccination Existing vaccines have proven efficacy but also have a high incidence of adverse side-effects. The risk of adverse events is sufficiently high that vaccination is not warranted if there is no or little real risk of exposure. Vaccine administration is warranted in individuals exposed to the virus or facing a real risk of exposure (see above). A safer vaccinia-based vaccine, produced in cell culture, is expected to become available shortly. There is also interest in developing monoclonal anti-variola antibody for passive immunization of exposed and infected individuals, which could also be administered to persons infected with HIV.
