Acellular pertussis vaccine may not provide long-lasting immunity

The acellular pertussis vaccine that was introduced in the 1990s may not offer long-lasting protection against whooping cough in immunized children after the fifth dose, according to a case-control study published September 13 in the New England Journal of Medicine.

Researchers from the Kaiser Permanente Vaccine Study Center assessed the risk of pertussis in children who received the fifth dose of the diphtheria-tetanus-acellular pertussis (DTaP) vaccine from 2006 to 2011. In this case-control study, 277 children who were between the ages of 4 and 12 years and polymerase chain reaction (PCR)-positive for pertussis, were compared with 3,318 PCR-negative controls and 6,086 matched controls.

The comparison showed that the PCR-positive children were more likely to have received the fifth dose of the pertussis vaccine earlier than the PCR-negative controls (P<.001) or matched controls (P=.005).

“Comparison with PCR-negative controls yielded an odds ratio of 1.42 (95% CI, 1.21-1.66), indicating that after the fifth dose of DTaP, the odds of acquiring pertussis increased an average of 42% per year,” the authors wrote.

“Protection against pertussis waned during the 5 years after the fifth dose of DTaP,” the authors concluded.

The study was funded by Kaiser Permanente.