In a period of more than 30 years during which modification of measles has been practiced on a large scale, very few children who had the modified disease developed measles on subsequent exposure. On questioning over 1,000 pediatricians and several hundred general practitioners, Karelitz1 collected only 22 reliable descriptions of measles occurring 7 months to 14 years after these children had the modified disease.
Townsend2 reported that 32 children who had had modified measles remained well upon reexposure 10 years later. Staff pediatricians1 of hospital services and of childcare institutions have noted that those children whose measles were modified by γ-globulin (G.G.) or convalescent serum (C.S.) did not develop measles on subsequent exposures. These observations indicate that modified measles does result in long-lasting immunity; nevertheless, many still question whether it does.
The development of reliable techniques3 for measurement of complement fixing and neutralizing antibodies to the