The agglutinin response to pertussis agglutinogens in diphtheria-tetanus-pertussis (DTP) vaccine was determined in human infants inoculated initially at ages four weeks to eight months. The effects of age at the time of initial dose and the interval between subsequent doses were specifically evaluated. Our findings demonstrate that optimum agglutinin production is best achieved with DTP vaccine by beginning immunization at five months of age or later followed by a second dose at eight weeks or more. Variation in the two variables, age and dose interval, decreases the likelihood of an optimum agglutinin response.
