Anti-vaccine advocates received a blow in New York Thursday as state lawmakers banned non-medical exemptions based on religious beliefs—and there may be more blows coming.

Also on Thursday, the American Medical Association adopted a new policy to step up its fight against such non-medical exemptions. The AMA, the country’s largest physicians’ group and one of the largest spenders on lobbying, has always strongly support pediatric vaccination and opposed non-medical exemptions. But under the new policy changes, the association will now “actively advocate” for states to eliminate any laws that allow for non-medical exemptions.

“As evident from the measles outbreaks currently impacting communities in several states, when individuals are not immunized as a matter of personal preference or misinformation, they put themselves and others at risk of disease,” AMA Board Member E. Scott Ferguson, M.D. said in a statement. “The AMA strongly supports efforts to eliminate non-medical exemptions from immunization, and we will continue to actively urge policymakers to do so.”

The religious exemption ban in New York comes at a critical time. The state is at the forefront of a nationwide resurgence of measles, with active outbreaks that have sickened hundreds and splintered into other states.

“This administration has taken aggressive action to contain the measles outbreak, but given its scale, additional steps are needed to end this public health crisis," New York Gov. Andrew Cuomo said in a statement after signing the ban on religious exemptions. "While I understand and respect freedom of religion, our first job is to protect the public health, and by signing this measure into law, we will help prevent further transmissions and stop this outbreak right in its tracks."

State laws allowing parents to opt their children out of otherwise required vaccinations have enabled some communities and schools to dip below the vaccination rates needed to keep disease from spreading. Eliminating the exemptions is aimed at boosting vaccination, protecting more children and communities from dangerous diseases, such as measles.

However, it’s not always that simple. In 2015, California eliminated non-medical vaccine exemptions following a large measles outbreak linked to Disneyland visitors. But in the years following, the state saw the number of children with medical exemptions triple. State health officials have blamed unscrupulous doctors writing bogus exemptions for anti-vaccine parents while charging hefty fees.

Lawmakers in California are now considering a new bill that would crack down on such bogus exemptions by granting state health officials oversight of any medical exemptions that doctors provide. Prominent anti-vaccine advocates, including Robert F. Kennedy Jr, have opposed the legislation. This week, actress Jessica Biel joined the fray, coming out on the side of anti-vaxxers. In an Instagram post, she incorrectly suggested that the additional oversight would make it harder for children who genuinely need medical exemptions to get them.