As the NFL prepares for a 2021 season that it hopes will be free of pandemic-related disruptions, more than 50% of the league's players have been vaccinated for the coronavirus.

But the league and the NFL Players Association continue to deal with vaccine wariness, employing an approach that stresses vaccine education and incentivizes players with the lure of relaxed protocols.

League leaders envision stadiums filled with fans this season, games played on schedule, and teams' lineups unaffected by testing results and contact-tracing quarantines. The degree to which the NFL can pull that off could depend in large part on the success that the league and the players' union have in their efforts to convince players to be vaccinated.

"Last season was certainly not normal," said Zachary Binney, an epidemiologist at Oxford College of Emory University. "You didn't have any games canceled. But you had games postponed. You had players being held out of games. All of those disruptions would be greatly reduced if you could get a large number of players vaccinated. I am certain the NFL knows this and is doing what it can to drive up vaccination rates. If no one got vaccinated, they could do what they did last year and have a season. But that was a pain."

The leaguewide rate of more than half of players being vaccinated (meaning they have received at least one vaccine dose) as of last week was confirmed by a person familiar with the situation. According to that person, 16 NFL teams have more than 50 of the 90 players on their rosters vaccinated. Three teams have 70 or more players vaccinated.

The teams not doing as well with their player-vaccination rates include the Indianapolis Colts, Jacksonville Jaguars, Arizona Cardinals and Los Angeles Chargers, according to that person, who spoke on the condition of anonymity because the league and NFLPA have not released player-vaccination rates.

"We've urged players to get the vaccine," DeMaurice Smith, the executive director of the NFLPA, said last week. "We've urged them to just make sure that they just make a decision that's informed."

The league has all but required that coaches get vaccinated, mandating that they do so to maintain the Tier 1 protocol status that enables them to work in proximity to players. But the NFL and NFLPA have stopped short of mandating vaccinations for players, even with significant potential competitive implications of teams having unvaccinated players looming.

"We're a microcosm of our country, right? ... There's wide disparities in our country between where some people are getting vaccinated and why some people haven't," Smith said in a video conference with reporters. "Look, I think the only thing that we can do is make sure that all of our players have all of the information. ... Nobody should not have all the information that they want. ... I don't think the country is in a place right now where we lack the information. I think the country is in a place right now where people are asking whether they trust the information and whether the information is sufficient to deal with any other issue they may have."

Washington Football Team defensive end Montez Sweat said last week that he was "not a fan" of vaccination efforts. Carolina Panthers quarterback Sam Darnold said he hadn't been vaccinated and had to "think about all those certain things that go into it."

Thom Mayer, the union's medical director, said last week he had spoken to many players about their concerns.

"The calls I field are not surprising," Mayer said. "They want to know: Did it go too fast? Why is it an emergency use authorization instead of the normal process that we go through? What is mRNA? Is that something that just got developed? ... So it's around that. I think there are people who worry about: Is this medical experimentation? Is it too fast? Is it too soon? What do we know? ... I can tell you, at least on the couple hundred folks that I've talked to, they are serious, thoughtful questions that deserve serious and thoughtful answers."

NFL Commissioner Roger Goodell said after an owners' meeting last month that the league and NFLPA had agreed to revised protocols differentiating between vaccinated and non-vaccinated players and personnel. Under those protocols, fully vaccinated players and personnel are not subject to daily testing, mask-wearing requirements, contact-tracing quarantines, travel restrictions or weight-room capacity limits.

"We do think that players and all personnel are safer if they're vaccinated," Goodell said then. "I think that's true throughout our country and throughout our world. I don't know of a single medical source that's respected that doesn't believe that and doesn't believe that vaccines not only work and [are] effective, but that they're also safe."

Fully vaccinated players and personnel are allowed to eat in team cafeterias, use saunas and steam rooms and interact with vaccinated family members and friends during travel. Non-vaccinated players and personnel remain subject to rigid protocols.

"My prediction: when unvaccinated players get to camp and see that their vaccinated teammates don't have to wear masks, can eat in the dining area, can hang out in the weight room, etc., many players who weren't going to get vaccinated will do so — incentives are very compelling," former Oakland and Los Angeles Raiders executive Amy Trask wrote on Twitter.

The league and union have discussed setting a per-team vaccination threshold — perhaps 85% — that would allow that team to shed many restrictions. Binney said in a phone interview that 85% is "probably reasonable" for such a threshold, but added: "What's important to keep in mind is that herd immunity is not an on-off switch. It's a dimmer switch."

Teams cannot cut players based on vaccination status. The league spoke to Buffalo Bills general manager Brandon Beane last month after he said publicly that he might consider releasing an unvaccinated player under certain circumstances. Yet there will be clear competitive implications once the season arrives, given how many players missed practice time and games last season based on testing results and contact tracing.

Coach Ron Rivera brought in a vaccine expert to address his Washington players. When asked whether he planned to do the same, Tampa Bay Buccaneers Coach Bruce Arians declared himself "the specialist" and said if players want to "go back to normal," they'll opt to be vaccinated.

Most NFL teams are scheduled to open their training camps July 27.

"I'll say what our players say: They're grown-ass men," Mayer said. "You give them the grown-ass facts and they'll make a grown-ass decision. I think what you're probably hearing is not that they don't have the information, but that it's a difficult decision for people to make."