HOUSTON -- The Mariners on Tuesday announced new COVID-related protocols for all events at T-Mobile Park, including mask mandates and plans for proof of vaccination requirements.

The announcement comes on the heels of Seattle & King County Public Health’s latest order that masks must be required for all outdoor gatherings of more than 500 people, effective immediately. The Mariners next play at home on Friday, when they return from this three-game series against the Astros in Houston.

The Public Health order applies to fans ages 5 and older in all locations of T-Mobile Park, including seats and concourses, but masks are not required while fans are actively eating and drinking. T-Mobile Park safety ambassadors will be present in various locations throughout the ballpark on game days to proactively encourage mask compliance, and single-use, multi-layer masks will be available at various locations in the ballpark for those guests who do not have their own.

The proof of vaccination policy won’t be installed until potential postseason games at the earliest. Seattle & King County Public Health on Tuesday announced plans for a vaccine verification policy that is likely to take effect in October.

“The evidence is clear -- vaccination is safe and effective in preventing serious illness from COVID-19. We are making this announcement now to give our season-ticket members and other fans the opportunity to get vaccinated before the requirement takes effect,” said Trevor Gooby, Mariners senior vice president of ballpark operations.

The NFL’s Seattle Seahawks, who open their home schedule on Sept. 19, and the NHL’s Seattle Kraken, who begin their preseason on Sept. 26, both announced proof of vaccination and mask mandates on Tuesday at their respective venues.

Also included in the Mariners’ announcement was that the club began notifying team employees on Aug. 20 that they are required to be fully vaccinated by Oct. 4 as a condition of employment. Employees have been required to wear masks at T-Mobile Park since Aug. 23.

This mandate applies to all front-office employees, event staff and team employees at Mariners-operated facilities across the country, including their Spring Training home in Peoria, Ariz., and Modesto, Calif., where their Low-A affiliate is located. It also applies to employees of vendors and contractors who work at T-Mobile Park, such as Centerplate, Allied Security, ABM housekeeping services and more.

This portion of the mandate does not apply to employees who are not at Mariners-operated facilities, such as remote-based employees like scouts. It also does not apply to employees covered by the Collective Bargaining Agreement, which includes players. Seattle is one of a handful of teams that has not reached the 85% vaccination threshold of Tier 1 personnel that allows for relaxed health and safety protocols. Tier 1 individuals include players.

“The Mariners are following the lead of an increasing number of organizations who believe mandating vaccination is the best way to protect employees,” the team wrote in a release. “With the spread of the highly transmissible COVID-19 delta variant across the U.S., infection rates among unvaccinated people, and a small number of vaccinated people, continue to rise. The evidence is clear that vaccination is safe and effective in preventing serious illness from COVID-19. Out of an abundance of caution, we believe it is necessary to take this step to more fully protect our employees, their families and our community.”