Studies with a further attenuated live measles-virus vaccine

A "further attenuated" live measles-virus vaccine was administered to more than 2,000 infants and children in the New York City area. The clinical and immunologic effects of further attenuated and Edmonston "B" vaccines were compared. Observations were made on the protective effect of live measles-virus vaccine. The febrile reaction rate following further attenuated measles-virus vaccine without gamma-globulin was 15%, a rate essentially the same as that following Edmonston "B" vaccine with gamma-globulin, 0.01-0.02 ml/lb body weight. The percentage incidence of fever in infants less than 2 years of age was 35%, a rate significantly higher than the 15% febrile reaction rate observed in older children. Modification of further attenuated vaccine by an additional inoculation of 0.2 ml of gamma-globulin eliminated febrile reactions almost completely; the "corrected" incidence of fever was 1%. A comparison of the relative incidence of febrile reactions following live measles, smallpox, and inactivated polyvalent influenza vaccines revealed no significant differences. Systemic reactions were most severe following influenza vaccine, minimal or absent following live measles vaccine, and moderately severe following smallpox vaccine. The following decreasing incidence of rash was observed when Edmontson "B" vaccine was modified by the addition of gamma-globulin and by further attenuation: Edmonston "B" vaccine, 50%; Edmonston "B" plus gamma-globulin, 12%; further attenuated vaccine, 5%; and further attenuated vaccine plus gamma globulin, 3%. The immunologic response following further attenuated vaccine without or with gamma-globulin (0.2 ml) exceeded 97%. A rapid immunogenic and protective effect of live measles-virus vaccine was observed in children from five families in which a case of measles had occurred. Vaccination performed on the day of exposure and 1, 5, and 6 days before exposure was followed by no illness and a significant antibody response. Children vaccinated 3 to 10 days after exposure acquired measles after the appropriate incubation period. The protective effect of live attenuated measles-virus vaccine was observed at the Willowbrook State School. Since the last "measles year" in 1960, 600 susceptible children were admitted to the institution; of this group, 550 were vaccinated. During the 1962 "measles year" only 32 cases of measles occurred in the entire institution—all in unvaccinated children.