Religious exemptions to vaccines elevates whooping cough rates


©Centers for Disease Control and Prevention, 2012
©Centers for Disease Control and Prevention, 2012

According to a new study published in Pediatrics, the number of New York state parents who skipped at least one required vaccine for religious reasons has increased over the past decade. And New York counties that had this increase in religious exemptions to vaccinations also had more  whooping cough (Bordetella pertussis, or simply pertussis) cases, even among children that had been fully vaccinated.

For this study, the researchers tracked data from the New York State Department of Health on both religious exemptions and new whooping cough cases. Children were reported as having a religious exemption if they had been allowed to skip at least one required vaccine for non-medical reasons. 

The key results from the study were:

  • The overall state annual mean rate of religious exemptions increased significantly from 0.23 % in 2000 to 0.45% in 2011, almost doubling the rate over the decade.
  • The prevalence of religious exemptions varied greatly among counties with no obvious trends, although all of the counties around New York City showed large increases in religious exemptions.
  • Counties with mean religious exemption rates of >1% reported a higher incidence of pertussis. For counties with higher exemption rates, the rate of pertussis was 33 per 100,000 compared to counties with lower exemption rates, which had a pertussis infection rate of 20 per 100,000. The researchers determined that this difference was statistically significant.
  • In addition, the risk of pertussis among vaccinated children living in counties with high exemption rate increased with increase of exemption rate among exempted children, also statistically significant.

The increase in whooping cough rates is particularly troubling since unvaccinated children not only put themselves at risk, but also those who have been vaccinated (as result of the lower effectiveness of the currently available pertussis vaccine). Also, as the exemption rate increases and there is a lower than expected effectiveness of the vaccine, the herd immunity becomes weaker. Continue reading “Religious exemptions to vaccines elevates whooping cough rates”