Authored By: Venkat Rao
Were National Football League (NFL) games a source for spread of COVID-19? A study just published in the Journal of the American Medical Association JAMA Network concluded with the answer: Yes. According to this study some games, depending on the in-person attendance policy set during 2020-2021 season, may have caused post-game spike in COVID-19 cases in the counties adjacent to the game venue. The study found county-level spike in COVID-19 cases associated with football fan attendance at the NFL games.
The cross-sectional study was based on data from all 32 NFL games during the 2020-2021 season attended by a total of 1.3 million football fans. According to the JAMA study, NFL games that had 20,000 or more fans in attendance had 2.23 times increase in rate of spike of COVID-19 cases, whereas NFL games with 5,000 or fewer fans in attendance did not generate a spike in the disease incidence. A key caveat to note in this study is the size of the in-person attendance—larger the fan attendance size greater the risk of spread of COVID-19.
Researchers mapped total COVID-19 cases and incidence rate at the county level using a one-, two- and three-week post-game attendance for each team game in the 219 host and surrounding counties. The one-, two-, and three-week post game periods for a total of 269 NFL games in the 2020-2021 created a total of 807 clusters comprised of 351 cluster of fans exposed by NFL games that allowed in-person game attendance and 456 clusters of unexposed fans to games that did not permit attendance in-person.
During 2020 and 2021 season only some NFL games were open to in-person attendance. Of the 269 NFL games 117 games allowed in-person attendance and 152 games were played without in-person attendance. The number of football fans attending in-person to 117 games ranged from a low 748 to as large as 31,700 persons at the Super Bowl 2021. The study found association between size of fan attendance with episodic spikes in COVID-19 cases. The study period was when Alpha and Beta SARS-CoV-2 variants were in transmission in the United States and before the emergence of the more highly transmissible Delta and Omicron variants.
Anecdotally soccer matches are believed to have played a crucial role in spread of COVID in the initial phase all over Europe. For example, Italian investigators on the impact of soccer matchers on spread of COVID-19, concluded soccer matches played in Italy during January and February 2020 contributed to the increased incidence of cases in March and April.
European soccer players were believed to have up to 3.5 times higher risk for COVID-19 during the initial phase of the pandemic. The study found incidence of COVID-19 among soccer players in Denmark was 9.9% compared to 3.7% in general population; Russian soccer players had a 14% incidence compared to 3.8% in general population; and Swedish soccer players had a 13.4% incidence compared to 7.2% in general population.
An earlier study in 2021 compared COVID-19 reported cases and mortalities across counties in the United States that hosted more NHL hockey games, NBA and NCAA basketball games during the early months of 2020 and found hosting one additional NHL/NBA game in March 2020 led to an additional 7,520 cases of COVID-19 and 658 deaths. Hosting one additional NCAA Division 1 basketball game in March 2020 resulted in an additional 34 deaths due to COVID-19. Preliminary estimates of per-game fatality costs were 200-300 times greater than per-game spending.
Other outdoor game events like the 10-day Sturgis Motorcycle Rally held in South Dakota, in 2020, were associated with outbreak of COVID-19 cases in Minnesota.
Recognizing the need to reduce risk of disease transmission at the games during the early phases of the pandemic, NFL had instituted mitigation protocols such as mask use and increased ventilation together with duration and proximity of interaction to reduce close interaction among the fans at the game to protect communities and minimize risk of COVID-19 transmission.
Nevertheless, like almost everything about COVID-19, several investigations in the same time period during the early phase of the pandemic contradict a link to large gatherings at NFL games with the spread of COVID-19. For instance, a study published in the Proceedings of the National Academy of Sciences, in March 2022, projected risk of COVID-19 transmission in 2021 NFL regular season based on 2020 NFL season fan attendance and concluded that opening stadium for in-person attendance had no impact on local COVID-19 case counts and that policy measures for outdoor sports events such as masking and distancing requirements counterbalance the risk of disease transmission among the fans in attendance. The robust statistical analysis making suitable corrections in previous studies for confounding factors on the opening of NFL stadiums to in-person fan attendance concluded no additional COVID-19 cases. Nonetheless, the study authors introduced a caveat stating that the study results reflected disease transmission rates and patterns in outdoor environments such as the NFL games before the emergence of more highly transmissible Delta and Omicron variants.
Another related study reached a similar conclusion on the potential impact of in-person attendance at NFL and National Collegiate Athletic Association (NCAA) games in 2020 and early 2021. Using an identical time-series cross-sectional study design to track COVID-19 cases at the county level before and after an NFL or NCAA game, in-person attendance was mapped to COVID-19 spikes in the adjacent counties. Mapping new reports of COVID-19 cases at the county level for up to 14 days post-game indicated that in-person attendance at NFL and NCAA resulted in no new excessive COVID-19 spikes to a significant level and was well within the average number of reported cases in comparable background population groups. Notably, a key caveat in the study was that no significant cases in COVID-19 cases was observed when NFL and NCAA games allowed limited in-person attendance.
How do we reconcile these apparently contradictory findings on the NFL game attendance association with community level spikes in COVID-19 cases? Were sport events in the United States and Europe responsible for a surge in COVID-19 during the early phase of the pandemic?
Crowd Gatherings Can Enable Infectious Diseases Transmission
There is nothing startling about large gatherings such as religious pilgrimages, sports events and music festivals causing increase infectious diseases outbreak. It is well documented phenomenon in the published literature. Large gatherings create an environment for close contact among participants which increases the risk of spread of infectious agents. Environmental degradation due to poor sanitary conditions, water pollution and unsafe food preparation due to demands placed by large events on the generally limited resources compounds the risk of disease transmission.
Interestingly, in the case of COVID-19, smaller gatherings such as having meal, family gatherings are more frequently and associated with disease transmission.
For instance, small-scale gathering of less than 100 people were more frequently linked to spread of COVID-19, than large-scale, outdoor sports gatherings such as NFL games. Respiratory viruses such as SARS-CoV-2 are transmitted via droplets generated by coughing or sneezing. Smaller size family get-togethers, parties and family events, gatherings in densely populated bars and restaurants are more frequent and less reported. Nonetheless, these events create conditions for extended person-to-person contact and exposure to airborne pathogens in breathing zone which is the most likely path of exposure to the virus and spread of COVID-19. Associative evidence linking a behavioral phenomenon to an observable endpoint such as in this case, COVID-19, are merely inferential with multiple other confounding factors at play. Researchers have pointed out among others public perception of risk of infection, or more relaxed policy measures granting in-person access to some games in some counties and not others may have attributed to a spike in COVID-9 cases in selected geographic areas. While acknowledging the risk of infection, more and more Americans are moving on from COVID-19. In a recent survey, nearly 65% of Americans accepted there is a small risk or no risk in returning to their normal, pre-COVID life. A more balanced consideration of public health risks is shaping up the national psyche as we chart a new post-pandemic course. Taking a cue from Albert Einstein, “A person who never made a mistake never tried anything new” lessons learnt in the course of COVID-19 pandemic should help us prepare and respond better when we confront the next health security challenge.