As of May 10, the CDC reported 839 measles cases in the United States with major outbreaks in several states, but California has seen just 42 cases, likely due to the strict laws it enacted in 2014, according to the Los Angeles Times.
As vaccine hesitancy took hold of Californians, immunizations rates dropped, reaching a low of 92.3 percent in 2013. The next year a measles outbreak occurred when an infected person visited Disneyland, which ultimately sickened 131 people in the state.
Lawmakers took immediate action to drive vaccinations. They passed laws that prevented parents from refusing vaccines for personal or religious beliefs. The two other states that do not allow people to opt out of vaccinations for personal or religious beliefs, Mississippi and West Virginia, have not reported any measles cases this year. On May 13, Washington joined their ranks with a law preventing parents from receiving personal or philosophical exemptions for the MMR vaccine for school-age children.
Parents in California can still opt out of the MMR vaccine due to medical conditions, and many are. Half of the state's counties have vaccination rates below 95 percent, which is the threshold for ensuring herd immunity.
Legislators are now considering a bill that would require the state to track medical exemptions to identify unnecessary or fraudulent ones.
The current measles case count of 839 is the highest in the U.S. since 2000, when the disease was declared eradicated in the country. Twenty-three states have reported cases this year.