Holiday travelers may assume that all public transit workers have been vaccinated against COVID-19. And in many cases, they have — but not all of them.

While the conductors and operators of the MBTA’s buses and subways are required to be vaccinated, that’s not the case on the region's commuter trains.

MBTA General Manager Stephen Poftak recently told the T’s Board of Directors that over 94% of the MBTA’s 6,500 employees are in compliance with a mandatory vaccination policy, and the remainder have requested an exemption due to either religious or medical reasons.

But there is no such mandatory vaccination policy on the commuter rail. That’s because Keolis, the company that operates the trains, is not part of the MBTA. It’s a private company contracted by the MBTA to operate the rail system.

“Keolis is continuing to strongly encourage its employees to get vaccinated, but will permit those who are unvaccinated to take advantage of a testing alternative,” the company said in a statement to GBH News.

Keolis employees are not subject to state regulations which require vaccinations. Instead, they follow federal OSHA rules and President Joe Biden’s vaccination mandate, which is scheduled to take effect Jan. 4. However, that mandate is still hung up in court, and it may be headed to the United States Supreme Court for a ruling.

Until legal questions around the federal mandate are resolved, Keolis workers are encouraged, but not required, to be vaccinated.

Earlier this week, some passengers at the Attleboro station who were waiting for a train to Boston said they did not know the commuter rail employees were subject to different regulations than MBTA workers, but they were not all surprised.

“There's a lot of companies that don't require vaccinations,” said commuter Caitlin Burke. But she added that she wished they would be subject to that requirement, saying, ”Yeah, that would be nice.”

Another commuter said the workers should be allowed to choose whether or not to get vaccinated.

"If they're going to put something into my body, then I should have the choice to choose yes or no,” said commuter Jason Gonsalves. "I don't think you should be vaccinated as long as you're taking all the health precautions like wearing a mask, keeping a distance and no physical touch.”

After their train pulled in, the group of commuters boarded, saying they didn’t feel unsafe riding the train and they would continue to do so whether there was a vaccine mandate or not.

Keolis said it is prepared to comply with OSHA’s COVID-19 requirements. Though the federal vaccination requirement still needs to be sorted out in the courts, Keolis said that all employees and riders are required to wear face coverings, and that the company maintains a supply of personal protective equipment for all employees including masks, hand sanitizer and protective eyewear.

Amtrak, the region's other train service, also does not require that employees be vaccinated. The company was planning a vaccine mandate for its employees but suspended it, averting the termination of about 500 people and service cuts that were expected next month. Amtrak railroad employees who aren’t vaccinated against the coronavirus will be allowed to submit to weekly testing instead.