The Houston Astros and Washington Nationals have mandated that all nonplaying full-time employees receive the COVID-19 vaccine, the first two teams in Major League Baseball to make vaccination a condition of employment, sources told ESPN.

The Astros were the first team to require compulsory vaccination and did so with their major league team as well as the three minor league teams they own, according to a source familiar with their policy.

Earlier this month, the Nationals told employees they would need to show proof of vaccination or offer a medical or religious exemption from receiving the vaccine. The deadline to provide proof was Thursday.

The vetting of exemptions is expected to continue into September, and employees without an exemption or proof of vaccine will be fired. The Astros declined comment through a spokesperson.

In a statement to ESPN, the Nationals said: "Like many organizations, the Washington Nationals decided to make COVID-19 vaccines mandatory for all full-time staff. Employees were notified of this policy on August 12 and had until August 26th to either provide proof of full vaccination, proof of first shot or apply for an exemption. As a company, we have a responsibility to do everything we can to keep one another safe and felt that mandating vaccines was the absolute right thing to do for our employees and our community."

Outside of baseball, vaccine mandates across professional sports in the North America have been far more prevalent. Multiple NHL teams have made vaccination for all employees mandatory, and the NBA on Friday said it would require a wide range of employees -- including the coaching, front-office and medical staffs along with any other person who might interact with a player -- to be vaccinated.

Multiple NFL teams have vaccination policies as well, and the NFL has proposed a vaccine mandate for players, something the NFL Players Association has pushed back against.

Vaccination rates around baseball vary. Around three-quarters of teams have exceeded the 85% threshold of Tier 1 employees -- which include players, coaches, medical personnel and others -- the minimum necessary for loosened restrictions on COVID protocols.

Employees working at Major League Baseball's commissioner's office are subject to a mandatory vaccination policy, and commissioner Rob Manfred said at the All-Star Game: "I'm a believer in vaccination. I understand that people have different views. I wish everybody gets vaccinated."

Neither the Nationals, who have had two COVID-19 outbreaks in their clubhouse this season, nor any other team can force players to get vaccinated because of the collective bargaining agreement that governs the player-team relationship. Manfred, when asked about a vaccine mandate for players, said: "I think [it] would be a good thing for us generally, but, you know, [we] work through with the people that represent the union."