In an effort to avoid further suspensions like the ones handed down to Tampa Bay Buccaneers wide receiver Antonio Brown and defensive back Mike Edwards, NFL officials spent the past week calling multiple teams to inquire whether players who had gotten COVID-19 had been vaccinated on site at the team's training facility or off site at another location, league sources told ESPN on Saturday.

League officials want further information on this in order to ascertain whether any other players have misrepresented their vaccination status, sources said. Teams have been leery about players using fake vaccination cards and have warned some of them about the severity of such an offense.

While there do not appear to be any active investigations over fake vaccination cards, the league wants to make sure no other players attempt to game the system.