1 The Department of Pediatrics, N.Y.U. School of Medicine, 550 First Avenue New York, New York
Mumps neutralizing antibody was transferred quantitatively across the placenta. Antibody was still detectable (
1:2) in 18 of 19 infants at 2 months of age. The finding of antibody in 13 of 19 infants at 5 months of age probably accounted for the failure to immunize infants at this age successfully in previous studies. Neutralizing antibody was not detectable sera of any of the 18 infants who were tested at 1 year of age. Although serum antibody during the early months of life was presumably all IgG since it was passively acquired, the neutralization test appeared to be far more sensitive than the complement fixation test for the determination of mumps antibody.