The incidence of pertussis in children rises steadily in the years immediately following receipt of the fifth dose of the diphtheria–tetanus–acellular pertussis (DTaP) vaccine, according to a study in Pediatrics.

Researchers examined the incidence of pertussis among more than 400,000 children in Minnesota and Oregon who’d received all five doses of DTaP, with the fifth dose given between ages 4 and 6 years. In the 6 years after the last dose was received, some 550 pertussis cases were identified. The incidence rose steadily with each passing year.

The authors say their findings “strongly [suggest] waning of vaccine-induced immunity,” which “helps to explain the emergence of an increased burden of disease among 7- to 10-year-olds.” (Currently, the adolescent booster is recommended at ages 11 to 12 years.)

Source: Pediatrics