Removing nonmedical vaccine exemptions improves herd immunity

BALTIMORE — Vaccine coverage among children entering kindergarten improved with more stringent state mandates that did not allow nonmedical vaccine exemptions, according to research presented at the National Foundation for Infectious Diseases’ Annual Conference on Vaccinology Research.

Researchers suggested that pockets of the country that allow nonmedical vaccine exemptions have eroded herd immunity, which can be fixed only with more stringent state-mandated school entry immunization requirements.

“Exemptions are important to examine in school-age children, and that is because the transmission patterns and long-term health effects are disproportionate,” Romain Garnier, PhD, DVM, a postdoctoral fellow in biology at Georgetown University, said in his presentation. “At school age, there are three ways parents can have their kids unimmunized, including medical, religious and philosophical exemptions.”

Garnier and colleagues examined CDC data on vaccine coverage rates and nonmedical vaccine exemptions for the beginning of the 2016-2017 and 2017-2018 school years. Information for 48 states and Washington, D.C., was available. The researchers also identified a subset of eight states that had changed their vaccination exemption policies. For these states, Garnier and colleagues compiled data on nonmedical vaccine exemptions for the school years 2003-2004 and 2017-2018.

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According to the researchers, both the rate of vaccination and the rate of nonmedical vaccine exemptions were strongly associated with the three major childhood immunizations that are mandated by schools: MMR, Tdap and varicella. Their analysis showed that the most effective way to increase immunization rates was by removing a certain type of nonmedical vaccine exemption, such as the removal of philosophical exemptions in Vermont, or all nonmedical exemptions, as California did.

In addition, Garnier and colleagues identified clusters of nonmedical vaccine exemptions at the county level. The only way to change that, they said, is “the most stringent policy change.”

“Strong policy changes can reduce nonmedical exemptions and maintain herd immunity,” Garnier said. “It is important to note that curtailing access to exemption is important because, otherwise, parents will seek alternative ways to get these exemptions.” – by Katherine Bortz

Reference:

Garnier R, et al. Policy changes in vaccine exemptions in the United States may shape herd immunity. Presented at: NFID Annual Conference on Vaccinology Research; April 3-5, 2019; Baltimore.

Disclosures: The authors report no relevant financial disclosures.