In late December, New York City instituted a mandate for private sector employers that, to work in the City, your workforce had to be fully vaccinated against COVID-19. This was done to ensure that one of the biggest, densely populated cities on the planet is as protected as possible from serious outbreaks and the resulting crises in hospitals and ICUs.
Today, the City confirmed that the Yankees and Mets fall under the same provisions as everybody else — that is, you cannot work in the City without being vaccinated. All mandates are subject to change with the constantly shifting state of the pandemic, but the City also confirmed that no individual exemptions would be given — any changes to the policy would be a change to the entire policy.