Arizona Gov. Doug Ducey issued an executive order on Tuesday that prohibits public universities and community colleges from requiring students to get COVID-19 vaccines or show proof of vaccination to attend class.

“The vaccine works, and we encourage Arizonans to take it,” Ducey said in a statement. “But it is a choice and we need to keep it that way.”

Although the executive order means universities in Arizona can’t require students to wear masks or participate in mandatory COVID-19 testing, Ducey included an exemption for students working in health care settings, such as hospitals, nursing homes, group homes and medical facilities. Those facilities are allowed to require health screenings and proof of vaccination.

In the event of a “a significant COVID-19 outbreak in a shared student housing setting that poses a risk to students or staff,” universities may require COVID-19 testing, but only if the Arizona Department of Health Services approves that testing first, the executive order states. The order, which has not yet been signed into law, does not prevent schools from encouraging vaccinations, providing testing or allowing students to wear masks voluntarily.

“In Arizona, getting the #COVID19 vaccine is a choice — not a requirement,” Ducey wrote on Twitter.

Ducey’s executive order may be in response to an announcement issued by Arizona State University on Monday.

“We are writing to remind you of the university’s expectation that all students enrolled in an on-campus academic program for 2021-22 will be vaccinated,” wrote Dr. Joanne Vogel, ASU’s vice president of student services. According to Vogel’s notice, students were expected to be fully vaccinated two weeks prior to the first day of class and to upload proof of vaccination to the school’s health portal. Unvaccinated students would be required to wear masks indoors and outdoors and undergo twice weekly COVID-19 testing.

On Tuesday, ASU issued a statement, saying that it would comply with the governor’s executive order and pushing back on the notion that there had been any vaccine mandate in the first place. “This week, we informed our student population of what to expect when they return to campus for the fall semester. We did not communicate a vaccine mandate.”

Arizona lags slightly behind the national average in vaccinations. As of Tuesday, 48% of residents had received at least one dose, and 38% were fully vaccinated, according to the Centers for Disease Control and Prevention. By comparison, 53% of Americans have gotten at least one shot and 44% are fully vaccinated.