Vaccine Study for Tick-Borne Encephalitis Virus (TBEV)

This was an open label trial of a non-US licensed vaccine for tick-borne encephalitis. The vaccine was licensed by Baxter, and now following an acquisition by Pfizer Inc in Vienna, Austria since 2001, and has an extensive safety record in multiple European countries. Field effectiveness studies suggest \> 99 percent protection against disease transmitted by the natural routes of either tick bite or ingestion of contaminated, unpasteurized milk. The vaccine is also considered to be effective against laboratory exposures and is used routinely for this purpose in European laboratories. The US Centers for Disease Control and Prevention and the National Institutes of Health acknowledge the effectiveness of the vaccine by allowing those who have received it to study tick-borne encephalitis virus (TBEV) in isolation facilities rated at BSL-3 rather than the more stringent BSL-4, with the exception of the Russian Spring-Summer Encephalitis strain. Subjects were recruited from personnel at 2 intramural campuses of the National Institute of Allergy and Infectious Diseases who may be exposed accidentally to any strain or serotype of viable TBEV. Approximately 160 individuals were eligible to participate. The rapid immunization schedule (injections on Days 0, 14, and 161) was used and subjects had labs drawn 21 days after the 2nd, 3rd and 4th vaccine injections to determine seroconversion. Subjects that seroconverted to TBEV were offered a booster dose of the vaccine 3 years from the date of receipt of the third dose of the vaccine. Subjects that were seropositive at entry into the study were offered a booster dose of the vaccine every 3 years from Day 0.