The effect of immunization against tetanus during pregnancy for protective antibody titres and specific antibody responses of infants.

The protective effect of immunization against tetanus during pregnancy was examined by determining the serum antitoxin titres in 28 infants of twice immunized mothers and in 39 infants of non-immunized mothers during pregnancy. In addition, it was also determined whether transplacentally passive immunization of infants exerts a suppressive effect on active immunization with DPT vaccine. Before primary immunization with DPT, serum tetanus antitoxin (IgG) titres higher than protective level of 0.1 IU/ml were found in 100 per cent of infants of mothers immunized during pregnancy. Thirty-one per cent of infants born to non-immunized mothers had serum tetanus antitoxin titres below the protective level. In the sera obtained 1 month after the third dose of DPT vaccine, no significant difference was observed between the infants of both groups of mothers. It was concluded that specific antibody responses to three doses of DPT vaccine in infants who had received passive immunity from their mothers were not suppressed, and administration of two doses of tetanus toxoid to women during pregnancy provided passive transient protection of the infant against tetanus before administration of first dose of DPT vaccine.