(HealthDay)—All 26,000 Houston Methodist workers must get a COVID-19 shot by June 7 or risk losing their jobs, making it the first U.S. hospital system to make vaccination mandatory.

Managers at the system were required to get their vaccinations by April 15, CBS News reported.

In March, Houston Methodist gave vaccinated workers an extra $500 and also warned that at some point the shots would no longer be voluntary. The includes a medical center and six .

"Mandating the was not a decision we made lightly, but science has proven that the COVID-19 vaccines are very safe and very effective," Marc Boom, M.D., Houston Methodist president and CEO, told employees on Friday in an emailed message, CBS News reported. "Like I say to everyone who asks—whether they are reporters, the public, patients, or our employees, it is our sacred obligation to do everything possible to keep our patients safe. By choosing to be vaccinated, you are leaders—showing our colleagues in what must be done to protect our patients, ourselves, our families, and our communities."

Boom also noted that he has "spoken to countless hospital leaders across the country who plan to mandate COVID-19 vaccination soon."

More information: CBS News Article