Current status of passive immunity to diphtheria and tetanus in the newborn.

The extent of transplacentally derived immunity to the toxins of Corynebacterium diphtheriae and Clostridium tetani was assessed by a hemagglutination technique using the cord sera of a group of infants recently born in Bronx, New York. Protective levels of antitoxin to C. diphtheriae were found in 64% of the infants. Tetanus antitoxin was present in sufficient quantity for protection in 38% of the cord sera. While this degree of immunity reepresents an improvement over that achieved 20 years ago and probably reflects the effects of immunization procedures, further attention to the maintenance of immunizations in women of childbearing age would improve these statistics.