General

After the discovery of the jungle form of yellow fever in Brazil in 1932, it became clear that this disease could not be fought simply by destroying the vector mosquitos or other carriers of the virus. Even before that date—in 1931—attempts had been made, using an effective vaccine,^'' * to immunize all laboratory staflF exposed to the risk of contracting yellow fever as a result of handling highly infective material. We shall not go into the details of the various types of virus vaccine and their methods of use, but shall restrict ourselves to a few remarks on the use of 17D virus vaccine for mass inoculation, particularly in the control of the violent epidemic outbreaks of yellow fever in Brazil. The first samples of 17D virus arrived in Brazil from New York in January 1937 and research with this type of virus began one month later. In March of the same year, production of the vaccine was begun in the laboratories of the National Yellow Fever Service. The vaccine was first tried out on a small number of laboratory staff, but was subsequently tested on a large scale in the southern part of the State of Minas Gérais.* Vaccination of 59,000 persons showed (a) that mild reactions occurred five to eight days after vaccination in 10%-15 % of the persons vaccinated, with more intense reactions in only l%-2 % ; and (b) that the vaccine was harmless even for children and for women at any stage of pregnancy. Laboratory studies indicated that the protective antibody generally appears in the blood towards the fourteenth day after vaccination. The results of protection tests carried out with a group of 882 vaccinated persons showed that about 95 % of them had acquired immunity. — 123