It’s flu season and many employers, particularly those in healthcare, want to require employees to be vaccinated to minimize the spread of illness. But what happens when an employee refuses on religious grounds?

The Center for Disease Control recommends that all U.S. healthcare workers get vaccinated annually against influenza, including not only those involved in direct patient care, but also those who can be exposed to infectious agents transmitted by others, such as food service, housekeeping, administrative and billing personnel. And for good reason: the flu can lead to hospitalization and sometimes even death. As the CDC says, you can get the flu from patients and coworkers who are sick with the flu and you can spread it to others even if you are symptom-free.

But when an employee objects on medical or religious grounds, an employer should tread carefully. Employers cannot require all federally recommended vaccines as a condition of employment. In fact, the EEOC recently filed suit on behalf of six former employees of a hospital who were fired after refusing the flu vaccine on religious grounds. The employer allowed such an exemption, but required employees to obtain a certification by a clergy member or other third party that the employee “practices a religion where influenza vaccination is contraindicated according to doctrine or accepted religious practices.”

That was their downfall. The employer wanted proof of accepted religious doctrine and the employees did not provide one. One was a Baptist who said that he had been instructed by God not to defile his body and that receiving vaccinations were a form of defiling the body. He cited Biblical passages in support of his request for exemption. Another claimed to practice “Christian Mysticism” and follow the teachings of “A Course in Miracles” which purportedly instructs that “when one obeys the laws of God, he will prevent disease, stay healthy and assist others in healing.” He cited those principles in support of his request. Another worker claimed to be a member of a non-denominational Christian faith and was not affiliated with a particular church, but still asked to be exempt from the vaccine on religious grounds.

We cannot predict the outcome of the EEOC’s lawsuit, but if an employer wants to avoid litigation, it must provide a reasonable accommodation for an employee’s sincerely held religious beliefs, no matter what those beliefs may be, unless it can show an undue hardship. And for their own protection, employers should consider requiring employees who refuse a flu shot to sign a form confirming that: they are aware of the risk of exposure; they have been offered the opportunity to have the flu shot; they have declined; and if they change their mind in the future, they can have the shot at no charge.