The NFL's chief medical officer notes that daily testing of all players for COVID-19, something the union's president has pushed for, has its strengths and weaknesses.

Using the situations for many doctors and nurses as a comparison, Dr. Allen Sills says testing is one component of fighting through the pandemic.

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"We know a lot more about testing and what the results mean," Sills told The Associated Press on Wednesday. "Remember we did over 1 million tests. We also learned the tests have some limitations. People who have been infected, for example, can continue to test positive long after they no longer are; that is one of the aftermaths of COVID-19.

"Doctors and nurses are not getting tested, that is something that is not recommended by the CDC. We have learned loud and clear that testing is not what keeps us safe, it is not prevention. We had some clubs with no cases in 2020 and others had scores of them. Clearly it was not how they were being tested — they all were being tested. It was the other (applications) such as masking and distancing and contact reporting."

Nearly 94% of NFL players are vaccinated, and Sills is encouraged by that number — particularly because of how that number has grown since midsummer.

"We're still working on vaccination education and we've been very clear that being vaccinated is very important for everyone and has the highest impact for health and safety," he said. "We still see people each week choosing to get vaccinated. Look at the numbers, half of the players who started out unvaccinated in camp have now started the process.

"We don’t see a finish line for that effort and hope to see those numbers improve as people become more comfortable with what our data are showing."

One thing the data show and the league is focusing on is symptom reporting. Sills stresses that it has been something of an overlooked topic, but its significance can't be overstated. The NFL will use multiple forums to get across that message, as it has done and continues to do about getting vaccinated.

"Symptom reporting is more important than ever," he said. "Vaccinated people may have very different symptoms. Last year, for those who had COVID-19, they might have a high fever and chills and trouble breathing ... and with the vaccination they may have only nasal congestion or a mild sore throat or a headache or fatigue.

"It's challenging to educate people to speak up about symptoms and get tests. Through our athletic trainers and physicians and coaching staffs, there is lots of communication going on."

As the only major sports organization that completed an entire schedule during the pandemic, Sills hopes the NFL provided guidance to everyone in all walks of life.

"We look at this holistically or globally, which is to say for all aspects of our protocols, in trying to create the safest possible environment and maximize protection," he said. "We are informed by what we learned last year: What keeps us and does not keep us safe.

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"I am much more optimistic than I was last year simply because we have safe and effective vaccinations we're able to deploy and create safer environments. There were so many things we didn’t know entering last season. We are in a much better place than last year and we have these important tools to use in this battle.

"I think our NFL experience will demonstrate a path forward for all of society."