(HealthDay News) – After receiving the last of five required doses of pertussis vaccine, a child’s protection from the disease rapidly declines, according to a study published in the Sept 13 issue of the New England Journal of Medicine.

Nicola P. Klein, MD, PhD, from the Kaiser Permanente Vaccine Study Center in Oakland, CA, and colleagues compared the risk of pertussis based on time elapsed since the last of five required doses of the diphtheria, tetanus, and acellular pertussis (DTaP) vaccine (before 7 years of age) in 277 children aged 4–12 years positive for pertussis (based on a positive polymerase chain reaction assay); 3,318 children negative for pertussis; and 6,086 matched controls. The study examined infection from 2006–2011, which included a large pertussis outbreak in 2010.

The researchers found that the pertussis-positive children were significantly more likely to have received their last DTaP dose earlier than both other groups. Compared with the pertussis-negative group, pertussis-positive children had an odds ratio of 1.42 per year for acquiring pertussis after the fifth dose.

“In conclusion, our evaluation of data from a large pertussis outbreak in California showed that protection from disease after a fifth dose of DTaP among children who had received only DTaP vaccines was relatively short-lived and waned substantially each year,” Klein and colleagues write. “Our findings highlight the need to develop new pertussis-containing vaccines that will provide long-lasting immunity.”

Two authors disclosed receiving grant support from the pharmaceutical industry.

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