As the N.F.L. makes plans to return to stadiums at full capacity this season, researchers published findings that “fan attendance at N.F.L. games led to episodic spikes” in the number of Covid-19 cases.
Major League Baseball, the N.B.A. and other sports leagues have started to let fans back into their stadiums and arenas, with most teams limiting attendance to 10 to 20 percent of capacity, but some allowing more. The N.F.L. has even grander plans. Last week, Commissioner Roger Goodell said the league hoped to open all of its stadiums at full capacity when the season kicked off in September.
“All of us in the N.F.L. want to see every one of our fans back,” Goodell said in a conference call with reporters.
Yet new research submitted to The Lancet, a scientific journal, in late March suggested that there was a link between the games that had large numbers of fans in the stands and an increase in the number of infections in locales near the stadiums. The study, which is being peer reviewed, is one of the most comprehensive attempts to address the potential impact of fans at N.F.L. games.
The authors, led by Justin Kurland of the University of Southern Mississippi, used the number of positive cases not just from the counties where the 32 N.F.L. teams play, but also from surrounding counties to track the spread among fans who may have traveled to games from farther away. After adjusting the figures to eliminate potential false positives and days when counties did not report cases, they found surges in infection rates in the second and third weeks following N.F.L. games that were played with more than 5,000 fans in attendance. The study does not prove a causal link between fan attendance and Covid-19 cases, but suggests that there may be a relationship between the two.
“The evidence overwhelmingly supports that fan attendance at N.F.L. games led to episodic spikes” in the number of Covid-19 cases, the researchers wrote.
Jeff Miller, the N.F.L.’s executive vice president for communications, public affairs and policy, said in an interview that public health officials in cities and states where N.F.L. teams play found no “case clusters” following the 119 games held with fans in attendance. Miller added that a study done by researchers at the M.I.T. Sports Lab, which was unpublished and independent, found no notable increases in Covid-19 infection rates “in the appreciable time frame following the games.” That study also looked at Covid numbers from surrounding counties but compared them to “synthetic” data used as a control group and found little difference between the two sets of numbers.
“Obviously, that was heartening,” Miller said.
Miller pointed to a study released by the Florida Department of Health that was not peer reviewed which determined Covid-19 infection rates were “slightly higher” in the Tampa area compared to the rest of Florida in the weeks after the city hosted the Super Bowl in February. A handful of people were infected after attending related N.F.L. events, but the state’s health department found that most transmission of the virus was “likely from private gatherings, in homes, or unofficial events at bars and restaurants.”
About 1.2 million fans attended N.F.L. games last season, as owners bet that the games would not inflame the pandemic any further. Teams sanitized their stadiums and asked fans to wear masks and sit away from other groups.
More than a dozen N.F.L. teams, including the three franchises in Florida and the two in Texas, hosted games with more than 5,000 spectators during the regular season. The Dallas Cowboys led the league in attendance in 2020, averaging more than 28,000 fans at its home games, followed by the Jacksonville Jaguars (15,919), Tampa Bay Buccaneers (14,483) and Kansas City Chiefs (13,153).
Kevin Watler, a spokesman for the Florida Department of Health in Hillsborough County, home to Tampa’s Raymond James Stadium, said contact tracers found “very low numbers” of positive coronavirus tests among people who attended Buccaneers home games during the season, and researchers do not believe those people spread the virus to others.
Dr. Rex Archer, the director of health for Kansas City, Mo., said health departments in the region detected no spread of the virus linked to Chiefs home games. The 1,000 or so fans who sat in club seats had to test negative to be allowed to attend, a requirement that prevented up to a dozen people per game from entering the stadium. Bars and restaurants, though, were harder to track because some were shut while others, particularly in neighboring Kansas, were not.
“You could have 15,000 socially distanced fans at Arrowhead Stadium, yet some people packed into a bar,” he said.
The league cited a separate study preprinted in February that showed that attendance at N.F.L. and college football games last season did not have a “significant” impact on the spread of Covid-19 but only tracked positive cases in counties where those games were held. The research submitted to The Lancet, however, tracked more extensive data from surrounding counties.
While Goodell is eager to see full stadiums in the fall, John Mara, the president of the Giants, was more measured. His team and the Jets will coordinate with the governor’s office in New Jersey before deciding how many fans can attend games at MetLife Stadium in East Rutherford during the 2021 season.
“As the vaccines continue to roll out, hopefully the positivity rate will be going down in the coming months,” Mara told reporters last week.
In a statement, Miller of the N.F.L. said the league would, as it did last year, follow the recommendations of local, county, state and federal public health officials, including the Centers for Disease Control and Prevention, and “continue to uphold with the advice and partnership of medical and public health experts as we look to the 2021 season.”
Trying to establish definitive causal links between a single event and a change in infection rates across a large metropolitan area is complicated. The authors of The Lancet study concede that their research only shows that two events — games with fans and increasing positive Covid-19 rates — coincided. Other events like political rallies, the reopening of colleges or holiday travel may have contributed to an increase in infections, especially in states where preventive measures like the wearing of masks were less widely adopted. Infections may have also increased because fans watched games with their friends in living rooms or at bars, gatherings that were beyond the N.F.L.’s control.
“The strength of these studies is they are showing something, but the correlations can only point out the possibilities, not the causation,” said Bruce Y. Lee, the executive director of Public Health Informatics Computational and Operations Research at City University of New York School of Public Health. “It’s not just a football game and people go home. There are all these associated activities around the game.”
To establish that N.F.L. games caused the spread of the virus, researchers would need contact tracing data on fans who attended games and then tested positive. That information is scarce, though, since many local health departments used their resources to educate the public on preventive measures and increase coronavirus testing. In Duval County, Fla., health officials said they did not study whether fans who attended Jacksonville Jaguars games were infected or whether the team’s home games increased the spread of the virus.
In part because not everyone cooperated with contact tracers’ requests, even people who attended N.F.L. games and tested positive had difficulty determining whether they got infected before, during or after the games.
Eight residents who tested positive for the virus told contact tracers that they had recently attended Cowboys home games, health officials in Tarrant County, Texas, said in November.
Researchers in the study submitted to The Lancet found spikes in the number of positive cases after games that had more than 5,000 in attendance, a reason, they argue, that leagues and event organizers should welcome back customers cautiously.
“We are not saying that the N.F.L. shouldn’t have opened up to fans,” said Alex Piquero, a sociologist the University of Miami and a co-author of the study. “But we have to understand the public health implications of opening up.”