Differences in antibody response to whole-cell pertussis vaccines

It has been assumed that whole-cell pertussis vaccines (WCVs) commercially distributed in the United States are of comparable immunogenicity, as all must comply with established standards for licensure. However, we have recently noted significant differences in antibody responses between groups of infants receiving the two WCVs commercially available in the United States. In separate studies performed concurrently under similar protocols at Vanderbilt and Johns Hopkins universities, infants were randomized to receive either an acellular pertussis vaccine or WCV. The acellular pertussis vaccine used at the two sites was identical, but the WCVs were from different manufacturers. Antibody responses to acellular pertussis vaccine did not differ between the two studies; responses to WCV differed dramatically, with infants receiving the Lederle WCV producing a 46-fold increase in antibody to pertussis toxin, compared with a 2.4-fold increase for infants receiving the Connaught WCV (P = .00003). Evaluation of other comparative data sets that were available provided further support for the conclusion that the two commercially available WCVs consistently differed in their ability to induce antibody to pertussis toxin. These findings have important implications for the design and interpretation of clinical trials comparing acellular and WCV products.