Adverse reactions and serologic response to a booster dose of acellular pertussis vaccine in children immunized with acellular or whole-cell vaccine as infants.

Adverse reactions and antibody response to pertussis toxin, ie, antitoxin, after a booster injection of an acellular pertussis vaccine were studied in 2-year-old children. A majority (212/241) of the children had previously been immunized with either two or three doses of the acellular vaccine at the ages of 6, 7, and 8 months. The other 29/241 children had received three doses of a plain whole-cell pertussis vaccine at the same ages. In the children who received primary immunization with the acellular vaccine, two cases of more serious systemic reactions occurred in close temporal association with the booster injection. Less serious systemic reactions were few. Local reactions were more common in the children only immunized with the acellular vaccine. Large reactions (greater than 10 cm) were only seen in this group. A good antitoxin response was elicited in both groups. The geometric mean titer in the former whole-cell vaccine recipients was significantly higher than in the children who received only acellular vaccine. The study raised some questions concerning differences in reactogenicity and immune response after a booster injection of an acellular vaccine depending on the type of pertussis vaccine given to infants for the primary immunization.