The protective effects of the DTaP vaccine wane, and prevalence of the disease is five times higher in children who had their last dose three years earlier.
Although vaccinated children are 13 times less likely to suffer from whooping cough than the unvaccinated, most cases are still happening among those who've had the DTP jab, say researchers at Kaiser Permanente.
Despite the media hysteria, the truth is that most children have had the five courses of the DTaP vaccine—designed to protect against diphtheria, tetanus and pertussis—designed for children aged between two months and six years. There was "high coverage" in the group of nearly 470,000 children tracked by the researchers; of these, 1 per cent of the children who developed pertussis were unvaccinated, and 3 per cent were under-vaccinated, which means they had not completed the full course.
But most of the children who developed the disease were fully vaccinated. Of the 738 pertussis cases in the group, 603 were fully vaccinated, 99 had not been vaccinated and 36 were partially vaccinated.
Coverage wasn't the problem, but the waning powers of the vaccine was, the researchers say.