Primary immunization of infants with an acellular pertussis vaccine in a double-blind randomized clinical trial.

The rate of adverse reactions and the immunogenicity of a two-component acellular pertussis vaccine as compared with a plain whole-cell vaccine and a placebo were evaluated for primary immunization in 319 6-month-old infants in a double-blind randomized clinical trial. The acellular vaccine produced few and mild systemic and local reactions. Fever (greater than or equal to 38 degrees C) occurred in 6% to 8% of acellular vaccinees as opposed to 25% to 37% of whole-cell vaccinees. Redness (greater than or equal to 1 cm) appeared in 2% to 13% of the acellular vaccine and 24% to 32% of the whole-cell vaccine recipients. Antibody response to pertussis toxin measured in a neutralization test was obtained in 97% to 100% of the infants receiving either two or three doses of the acellular vaccine as compared to 59% after three doses of whole-cell vaccine.