Effect of passive immunity to tetanus in DTP vaccinated infants.

Tetanus antitoxin levels in DTP unvaccinated and vaccinated infants whose mothers had either received no dose or two doses of absorbed tetanus toxoid at present pregnancy were determined by the enzyme immunosorbent assay (EIA). It was found that the percentage of protective infants born from non-immunized and immunized mothers were 95.4 and 100 respectively. The transplacental tetanus immunity in infants of immunized mothers was higher than those of non-immunized mothers, however, it was significantly reduced in both groups of infants within two months. After the first dose of DTP vaccine, infants born from non-immunized mothers were able to respond well in producing antibody whereas the infants from immunized mothers were not. In the second and third dose of DTP vaccine both groups of infants had a similar range of tetanus antitoxin.