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KANSAS CITY, Mo. — News that Kansas City Chiefs wide receiver Josh Gordon tested positive for COVID-19 and was placed on the reserve/COVID-19 list Monday afternoon surprised fans. But Gordon might have been as shocked as anyone.

He tweeted hours after news of his positive test was made public. His message for followers was to get a COVID-19 booster.

“Vaccinated & all.. Smh damn. I think it’s just a winter sniffle. Where’s the booster. #GetVaccinated #Stay Safe,” Gordon tweeted.

Gordon was one of 36 players to test positive in the latest round of testing, the NFL announced Monday afternoon.

Due to the number of positive tests, the NFL said it will require coaches and other tier 1 and tier 2 individuals who have previously received the vaccine to get boosters. The mandate doesn’t apply to players because discussions with the NFL Players Association are ongoing.

Last month, the NFL required players and staff to wear masks inside team facilities regardless of vaccination status for a week, and ordered they be tested twice for COVID-19 after the Thanksgiving holiday.

The league’s protocols then were updated as a result of increasing rates of COVID-19 across the country. At the time, nearly 95% of NFL players were vaccinated, and almost 100% of NFL personnel were vaccinated.