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Recent changes in California vaccine exemption laws projected to have limited effect on increasing childhood vaccination rates

November 5, 2019

In 2015, California passed Senate Bill 277 (SB277), which banned nonmedical exemptions from school-entry vaccine mandates. However, in the first 3 years after SB277 was passed, rates of both medical exemptions and students who were exempt from requirements and not up to date on vaccination increased. In response, California passed Senate Bill 276 (SB276) in 2019, adding additional scrutiny to medical exemptions.

A new study finds that the laws developed in California to decrease the number of children who are exempt from receiving vaccines may have little effect. This is because parents motivated by a hesitancy to vaccinate continue to find alternate pathways around the laws. Findings from the brief research report are published in Annals of Internal Medicine.

Paul Delamater
Paul Delamater

Led by Paul Delamater, Assistant Professor of Geography at the University of North Carolina at Chapel Hill and a fellow at the Carolina Population Center, a group of scholars studied publicly available data on vaccination and school enrollment to estimate the percentage of California schoolchildren with an exemption from vaccination from 2015 to 2027 under three different scenarios: 1) current exemption use continues (no SB276); 2) the potential effect of SB276; or 3) a hypothetical scenario in which neither SB277 or SB276 was implemented (for comparison).

The researchers estimate that a large percentage of California schoolchildren will continue to be exempted from vaccination, even after the passage of the new laws.

“We found that if current rates of medical exemptions and students exempt from requirements continued into the future, then the effect of SB277 on students with any type of exemption would be quite small,” says Delamater.

These findings demonstrate how the persistence of vaccine hesitancy and alternate pathways to avoid vaccination may mitigate the effects of efforts to increase vaccination coverage in schools.

“If policymakers want to reduce exemptions, they should make sure they do not provide alternate pathways to avoid vaccination,” says Delamater. “In California, SB277 removed the option for nonmedical exemptions, but it also relaxed the requirements for medical exemptions and exempted students in nonclassroom-based learning environments from vaccination requirements. Because of these provisions in SB277 and persistent vaccine hesitancy in California, the law’s effect has been and will continue to be limited.”


Alison Buttenheim and Salini Mohanty of the Department of Family and Community Health, University of Pennsylvania School of Nursing; Nicola P. Klein of the Kaiser Permanente Vaccine Study Center; of the Department of International Health, Johns Hopkins University; and Saad B. Omer of the Yale Institute for Global Health, Department of Medicine, Yale School of Medicine, Department of Epidemiology of Microbial Diseases, Yale School of Public Health also contributed to the study, which was funded by grant R01AI125405 from the National Institutes of Health (NIH).