Enders' live attenuated measles-virus vaccine 1 has provided the key to control and possible eventual eradication of this most important disease of childhood. The numerous studies now recorded have shown the uniform effectiveness of the vaccine for inducing neutralizing and CF antibodies in susceptible children, and Krugman et al.2 and Hoekenga et al.3 have demonstrated conclusively that the vaccine given alone affords protection against the natural disease in epidemics. The vaccine virus, even though markedly attenuated, still has the drawback of causing significant clinical reaction, primarily in the nature of rash and fever. These reactions are sufficiently great to preclude general patient and physician acceptance. Consequently, further modification of vaccine reaction is needed.
Early efforts by our group4 to modify the clinical response by administration of vaccine to babies who had maternal antibody were unsuccessful because of apparent total neutralization of the virus. Failing this, vaccination was