The NFL is taking more steps in an attempt to stop the spread of COVID-19 around the league.

In a memo sent Monday to all teams the league explained that all Tier 1 and Tier 2 employees must receive a booster shot by December 27, according to Pro Football Talk.

Tier 1 includes players, coaches, and trainers; however, the league says that players do not fall within the scope of the memo. Tier 2 includes general managers and football operations employees, among others.