The following graph shows the percentage of enrolled kindergartners with medical exemptions, personal belief exemptions and total exemptions in California from 2000 to 2016. Total vaccine exemptions dropped sharply following the 2016 implementation of a state law that eliminated the exemption for personal beliefs. But researchers say a spike in medical exemptions — which more than tripled to 2,850, from 931 the previous year — could suggest that vaccine-reluctant parents are simply finding doctors who are willing to write them medical excuses.