More parents are seeking vaccination exemptions for their children on religious grounds, and now a new study has found that such faith-based applications are even higher in states that don’t permit “personal belief” exemptions.

States that allowed both religious and personal belief exemptions were less likely to have kindergartners with religious exemptions than states with only religious exemptions, according to the study published Monday in the journal Pediatrics.

The findings come at a time when leaders of virtually all major religions have advised their members to get their children immunized.

“In our study, kindergartner religious exemption rates differed by personal exemption availability, being four times more likely in states with religious exemptions compared to states with both religious and personal belief exemptions,” said Joshua T.B. Williams, lead author of the study and a pediatrician with the Denver Health Medical Center.

All states require some vaccinations for schoolchildren, particularly for highly infectious, preventable diseases like measles, mumps, and rubella. Every state also allows medical exemptions for children who cannot safely receive the vaccines. Forty-five states allow religious exemptions and 15 states, including Pennsylvania, also permit exemptions for personal beliefs.

New Jersey allows religious and medical exemptions, but not exemptions on the grounds of personal belief.

Analyzing data from the federal Centers for Disease Control and Prevention, the researchers found that religious exemptions crept upward overall from the 2011-12 school year to 2017-18.

To gauge the impact of eliminating the personal belief exemption, the researchers looked at what happened in Vermont, which did that in 2016.

As they suspected, the researchers found a replacement effect.

“The rate of religious exemptions among kindergartners increased from an average of 0.5% per year to 3.7% per year,” Williams said. “Put differently, from roughly one in 200 kindergartners to nearly one in 25 kindergartners.”

» READ MORE: New Jersey study finds exemptions rose by more than half in five years

Recent years have seen a rise in vocal opponents to immunization who believe vaccines pose health threats, though no scientifically credible research has found evidence of such harms. Not vaccinating youngsters, health officials say, fueled the measles outbreak this year that recorded the highest number of cases in the United States since 1992. Pennsylvania and New Jersey were among the 31 states that saw a resurgence of measles in the past year.

Pennsylvania and New Jersey have also seen their vaccination exemption rates rise. A study released this summer by the New Jersey Hospital Association found that the number of Garden State children whose families claimed religious exemptions from vaccination jumped nearly 53% in the last five years. The religious exemption rate rose from 1.7% in the 2013-14 school year to 2.6% in 2018-19.

Pennsylvania’s nonmedical exemptions also rose, according to state data. The religious exemption rate in the 2015-16 school year was 1% and the philosophical exemption rate was 1.3%. In 2017-18, the religious exemption rate was 1.3% and the philosophical exemption rate was 1.7%.

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Both states’ vaccination rates are still within the range experts say is sufficient for “herd immunity” — the rate of immunization necessary to keep contagious diseases children are vaccinated against from becoming widespread. Both states’ legislatures have proposed bills that would limit exemptions.

The Denver researchers say more study of exemptions is warranted. While religious exemptions have increased, they said, previous studies indicate that fewer Americans identify themselves as having a religious affiliation, yet more say they consider themselves to be spiritual.

“It may be that insular religious groups are growing more rapidly than secular communities, or that they are increasingly falling victim to vaccine misinformation,” the study said. “Yet the rise in religious exemptions in an increasingly secular society also questions whether the religious exemption category can still serve its intended purpose.”