HOUSTON -- Astros third baseman Alex Bregman, designated hitter Yordan Alvarez, catcher Martín Maldonado and infielder Robel Garcia are scheduled to fly to Colorado on Monday and be activated in time for Tuesday’s game against the Rockies, a source told MLB.com.

Bregman, Alvarez, Maldonado and Garcia will have to clear more tests once they arrive in Denver, but should be available to play Tuesday night. Second baseman Jose Altuve, who along with those four players was placed on the COVID-19 injured list Wednesday, remains on the IL and won’t travel. Mark Berman of KRIV-TV in Houston broke the news.

Tuesday’s game against the Rockies in Denver remains on schedule despite a winter storm that is forecast to hit the area Monday and push temperatures to record lows. The Astros have yet to announce a starting pitcher.

The Astros had one player, relief pitcher Pedro Báez, test positive for COVID-19 during the spring, which forced a group of pitchers into quarantine in March. The Astros left Spring Training and flew from Florida to Houston on March 29 to get vaccinated as a team at Minute Maid Park.

The Astros are trying to work the logistics of getting players their second vaccines while safeguarding against what the side effects could potentially do to their roster.

Clubs were informed just before Opening Day that MLB and the MLBPA have agreed to relax certain health and safety protocols contained in the 2021 Operations Manual for fully vaccinated Tier 1 Individuals and for clubs once 85 percent of their Tier 1 Individuals are fully vaccinated. This applies to all players and staff who are considered Tier 1, including those at the alternate site. As part of that memo, players and staff were again strongly encouraged to receive one of the approved COVID-19 vaccines when eligible.

Astros general manager James Clickremains optimistic the Astros will hit the 85 percent threshold.