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Observed Versus Expected COVID-19 Infections Among National Football League Players During the 2020 Season

Our take —

When comparing observed to expected cases among US National Football League players during the 2020 regular season, the study found that the observed cases were 55% lower than expected. During the season, the NFL put in place a number of mitigation strategies, including daily testing and masking, that may explain this observed result. Comparing NFL players to the general community in terms of COVID-19 cases may be problematic, however, because of differences in socioeconomic status, underlying health, and race. Further, results precede the emergence of the Delta variant and widespread access to the vaccine, both which may affect risks, though in opposite directions. Overall, these data suggest that with intensive mitigation strategies, at least pre-Delta, return to safe play of sports is possible. High rates of vaccination coverage among NFL players (93%) may further increase safety in the upcoming 2021-2022 season.

Study design

Other

Study population and setting

To quantify the impact of holding a regular National Football League (NFL) season on infections among players, observed versus simulated expected cases of COVID-19 among players were compared during the 2020 football season. There were 32 teams who played 256 regular season games, and additionally met for meetings and practices. Between August 1, 2020, and January 2, 2021, the expected number of infections was estimated in a population with similar age and sex using county-level COVID-19 test data for each team (New York Times positive test counts for each day). A binomial distribution was used to simulate expected cases and compare these to observed COVID-19 infections in players. Given that daily testing was being done among the players but not in the general population, an inflation factor (based on CDC estimate for the beginning of the period) of 6.5 (95% CI: 3.5-12.4) cases per positive test was applied to the expected case counts.

Though a “bubble” was not utilized by the NFL (restricting contact between players and the outside community), a number of mitigation strategies were put into place to prevent the transmission of COVID-19, including: daily testing (RT-PCR), mandatory masking, quarantine and isolation, and others.

Summary of Main Findings

Overall, when comparing observed (n=256) to the expected (n=578) simulated cases, it was found that observed cases were 55.7% (95% CI: 53.2%-58.1%) lower. 30 of the 32 teams fell at or below the expectations, while 2 teams had a greater number of cases than expected. Data from 2020 precede the emergence of the Delta variant, which may reduce effectiveness of mitigation strategies and alter the risks faced.

Study Strengths

A strength of this study is that there was daily testing and complete follow-up data on all the players during this period.

Limitations

One major limitation is that NFL players are different from the general population in a number of ways (socioeconomic status, underlying health/fitness, and/or diet, race/ethnicity, etc.) that this study does not take into account. Some of these differences may partially explain the difference in observed vs. expected cases.

Value added

These results support the understanding that testing and behavioral mitigation strategies can facilitate a return to normal activities while limiting the spread of COVID-19.

This review was posted on: 21 September 2021