A single San Diego doctor wrote nearly a third of the area’s medical vaccination exemptions since 2015, according to an investigation by the local nonprofit news organization Voice of San Diego.

The revelation follows growing concern that anti-vaccine parents are flocking to doctors willing to write dubious medical exemptions to circumvent the state’s vaccination requirements. Since California banned exemptions based on personal beliefs in 2015, medical exemptions have tripled in the state. The rise has led some areas to have vaccination rates below the levels necessary to curb the spread of vaccine-preventable illnesses. Moreover, it signals a worrying trend for other states working to crack down on exemptions and thwart outbreaks of vaccine-preventable diseases. There are currently six outbreaks of measles across the country.

Medical vaccination exemptions are intended for the relatively few people who have medical conditions that prevent them from receiving vaccines safely. That includes people who are on long-term immunosuppressive therapy or those who are immunocompromised, such as those with HIV or those who have had severe, life-threatening allergic reactions (e.g. anaphylaxis) to previous immunizations. Such patients typically receive medical exemptions incidentally during their medical care. But some doctors are providing evaluations specifically to determine if a patient qualifies for an exemption and granting exemptions using criteria not based on medical evidence. Some doctors are even charging fees for these questionable exemption evaluations—including the doctor in San Diego, Tara Zandvliet.

Zandvliet’s practice website specifically lists “Evaluation for Medical Exemption to Vaccination” as a service provided. The website also lays out the conditions and diseases she considers as qualifying for a medical exemption. The list reaches far beyond what medical experts say are acceptable reasons for exempting someone from life-saving immunizations. The list includes having a family history of bee-sting allergies, type I diabetes, or simply hives. After a reporter with the Voice of San Diego questioned some of the conditions listed, Zandvliet removed three from the list: asthma, eczema, and psoriasis.

“I have found that a few of the diseases on my list seem to invite misinterpretation more than others, and so I have deleted them,” she told the outlet in an email.

Zandvliet charges $180 for the evaluation, and her practice does not accept insurance.

Since 2015, Zandvliet has issued 141 of the 486 total medical exemptions granted in the San Diego Unified School District. After Zandvliet, the second highest number of medical exemptions granted by a single doctor was 26. The Voice of San Diego noted that Zandvliet’s practice is listed on several websites as being friendly to anti-vaccine parents.

As Ars reported last month, Democratic state Sen. Richard Pan, who wrote the initial ban on nonmedical exemptions, is now working on legislation to thwart phony medical exemptions and crack down on physicians handing them out. “I think we need the health departments to basically say when someone is abusing [their] authority—and to withdraw that authority and invalidate exemptions that were fraudulent,” Pan told CALmatters.org.