Major League Baseball will not require minor league players to be vaccinated against COVID-19 to play in 2022 but will mandate on-field staff working with players be "up-to-date" on vaccinations, according to a memo sent to teams Thursday morning and obtained by ESPN.

The league had considered mandating vaccinations across the minor leagues, which it could have done without players' consent because their working conditions are not governed by a collective bargaining agreement like major leaguers.

Ultimately, MLB decided against it, though it did put conditions into place for managers, coaches and others who will have in-person contact with players.

The standard for "up-to-date" vaccinations is that those eligible for a booster shot have received one and those who have not been vaccinated can receive a Pfizer or Moderna shot before reporting to spring training and have another scheduled to be in compliance. Additionally, the memo said, "only bona fide religious and medical exemptions requests may be considered by Clubs."

In a statement to ESPN, the league said: "Our expert consultants have advised that fully up-to-date vaccination of all on-field staff and others with close player contact provides a safer environment in which to prevent infection and transmission. Reasonable accommodations will be considered for staff members who receive an exemption to this requirement. Such exemptions will be considered on an individual basis and in accordance with state law. We continue to strongly encourage vaccination among Minor League players and make resources available to Minor League teams and players toward that goal."

Around 88% of minor leaguers were vaccinated during the 2021 season, according to a league official, a number that mirrored the percentage of players and staff vaccinated at the major league level. COVID-19 protocols at the major league level are decided by the league and MLB Players Association.

Baseball's calendar has played in its favor over the past two months, as the omicron variant ravaged NFL, NBA and NHL rosters and caused the postponement of games. The recognition that players are younger, generally healthier and, according to doctors, at less risk for severe infection played into the decision not to mandate vaccination, sources said.

Vaccinated players in the minor leagues, the memo said, "likely will be subject to some -- albeit less restrictive -- testing and health and safety protocols." Their unvaccinated teammates, according to the memo, "will be subject to increased regulation and prohibitions, including the requirement to conduct intake and regular surveillance testing, mask wearing, and restrictions on their access to Restricted Areas."

Minor league players and staff are expected to report to spring training at the regularly planned time -- for most in late February.

The memo, which addressed a number of issues in addition to COVID-19 protocols, said that despite the lockout that is approaching its second full month, teams "may not adjust their previously scheduled Minor League Spring Training dates as a result of the work stoppage at the Major League level."