Almost twice as many parents in New York sought religious exemptions from vaccination in 2011 compared to 12 years earlier, and cases of whooping cough (pertussis) increased simultaneously, according to new research in the journal Pediatrics. As the number of children who are not given the pertussis vaccination increases, so does the risk that all children in the community will contract the highly contagious respiratory disease, the study found.

Investigating the impact on all children when some families exercise the right to opt-out of required vaccines for religious reasons, it was discovered that counties with exemption rates of at least 1% experienced higher rates of whooping cough — in both unvaccinated and vaccinated children — 33 cases per 100,000 children on average compared to 20 cases per 100,000 in counties with lower exemption rates, according to the authors.

The prevalence of religious exemptions varies among counties in New York, but it increased during the past decade, according to the authors, who note the need for awareness regarding the risks to the community of individuals opting out from recommended vaccinations.