MULTIPLE ANTIGEN IMMUNIZATION OF INFANTS AGAINST POLIOMYELITIS, DIPHTHERIA, PERTUSSIS, AND TETANUS

Abstract

This study was designed to determine the earliest age in infancy at which immunization against poliomyelitis, diphtheria, tetanus, and pertussis can be started using a multiple antigen containing component antigens against all four diseases. Subjects ranged in age from 1 day old through 6 months old at time of initial injection. All were given a series of four injections of 0.5 ml of DPT-polio antigen 4 weeks apart followed by a fifth dose (0.5 ml) of the same material 6 months later. A control group received 0.5 ml of a DPT antigen at monthly intervals for their first four doses, but were given a DPT-polio injection (0.5 ml) for their fifth dose. Although it is evident that there is a progressive response in relation to age of the infant at time of initial inoculation, in respect to poliomyelitis and pertussis immunization, it was apparent that the capacity of the 3-month-old infant to respond to active immunization closely approximates that of the 6-month-old. Ninety per cent showed definite evidence of an immune response to all three poliovirus types despite extremely high levels of preprimary maternal antibody in the majority of 3-month-old infants under study. Pertussis antibody response, as measured by agglutinin titers, was as good in the 3-month-old as in the 6-month-old infants. The response in the 2-month-old infants was relatively poor at the postprimary stage but was equivalent to that of the older infants at the postbooster interval. There was no indication that response to pertussis immunization was impaired by the inclusion of pertussis antigen in the quadrivalent antigen under study. Diphtheria and tetanus antitoxin titers were excellent regardless of age at initial inoculation. The results indicate that four doses of DPT-polio combined antigen given at monthly intervals will overcome the interference of high levels of maternal antibody in respect to poliomyelitis immunization and that the primary series of injections may be started as early as the third month of life. It is important, however, that this primary series of inoculations be followed by a booster dose of the same antigen preparation in about 6 months in order to reinforce the basic immunity.