Immunization Against Yellow Fever

Abstract

Summary 1. Protective antibody against yellow fever virus is demonstrable in the serum of rhesus monkeys within 6 or 7 days after inoculation with standard 17D yellow fever vaccine virus. 2. Rhesus monkeys are completely resistant to the inoculation of highly virulent pantropic yellow fever virus within 5 or 6 days after injection of 17D vaccine. This resistance is present prior to the appearance in the serum of demonstrable protective antibody. 3. Protective antibody is demonstrable in man in a high per cent of cases by the 10th day after injection of 17D vaccine and may be present as early as the 7th day. 4. Postvaccination surveys of immunity were made in persons inoculated in Africa with 17D vaccine prepared in New York, and revealed the following: a. 92.2 per cent of military personnel sampled 1 to 22 months after vaccination exhibited protective antibody. b. 90 per cent of civilians inoculated in Kenya exhibited protective antibody in their sera 23 to 36 months after receiving the vaccine. c. More than 90 per cent of persons vaccinated in Uganda had protective sera after 3 years, and there was no decline in the incidence of immunity during the third year. d. The percentage of children who became immune as the result of inoculation was as great as that in adults, and the antibody response was equally well maintained.