A new study published in JAMA Pediatrics says it will take California a full six years before the benefits of its new school vaccination law will be fully realized. The new law (Senate Bill 277), which takes effect July 1, 2016, eliminates all but medical vaccine exemptions from school vaccination requirements.

The number of students in California with “grandfathered” exemptions in public and private schools will, however, remain as high as 95,090 in 2018 and 37,224 in 2020 (1.39 percent and 0.54 percent, respectively), according to the study’s authors.

Their analysis of immunization and school enrollment data found that while students with nonmedical exemptions will begin steadily declining this year, it will be 2022 before they are fully eliminated from the school system.

The California Medical Association (CMA) sponsored SB 277 to overhaul what had been one of the country's most permissive vaccine-exemption systems, turning it into one of the most protective.

Personal belief exemptions submitted prior to January 1, 2016, however, will remain valid until the exempted child enters kindergarten or seventh grade. Only children with underlying medical conditions are exempted from being fully vaccinated before starting school.

Vaccine uptake for school-age children in California varies considerably depending on the neighborhood, and some schools still have more than half of the student body covered by the grandfathered personal exemption. Counties with a higher proportion of vaccine exemptions experience greater disease incidences in both exempted and vaccinated children.

As if to illustrate this point, the Associated Press reported last week that the Yuba River Charter School in Nevada City was closed on Tuesday after an unvaccinated child was diagnosed with measles. Nevada County health officials say the child was infectious while attending the school on March 17.

Nevada County has one of the lowest child vaccination rates in the state. Only about 43 percent of kindergarten students who entered school last fall had up-to-date vaccinations. Yuba River Charter School resumed classes on Wednesday, but students unable prove immunity to measles can't return until April 8.

The study’s authors estimated that 2.47 percent of California's school-going population, or 165,165 students, remained unvaccinated for nonmedical reasons in 2015. To calculate 2015–2022 nonmedical exemption data, the researchers used Immunization Assessment Results from the California Department of Public Health and projected enrollment from the Department of Education.

CMA, along with the American Academy of Pediatrics, California, and the California Academy of Family Physicians, developed an FAQ that provides information on what physicians need to know about SB 277 and vaccination laws.