Bumper crowd for USA’s Indy 500 highlights dangers of unmasked crowds and need for vaccinations

The Indianapolis Motor Speedway’s hosting of the largest sporting crowd in the world since the start of the Coronavirus pandemic for the Indianapolis 500 has highlighted the dangers of mass gatherings and the risk of COVID-19 infection.

Held on Sunday 30th May during the USA’s Memorial Day Weekend, the 105th running of the Indy s 500 saw 135,000 spectators in attendance.

However, images from the famous motorsport event showed that only a small proportion of fans appeared to be adhering to guidelines on wearing masks and social distancing.

Prior to the event, Indianapolis Motor Speedway (IMS) executives had told attendees that they must wear masks at all times, except when eating and drinking, and also said that there should be space between different groups of fans.

However, officials acknowledged last week that there was a danger of spectators refusing to comply with the rules and, as a result, ‘mask ambassadors’ were deployed to circulate through the stands, holding signs to remind people about the regulations.

Against these fears, John E. McCarthy, a Washington University in St. Louis mathematician, provided a simple, evidence-driven answer to two questions about the race crowd: How many were vaccinated? How many were safe from COVID-19 transmission?

Concluding “not enough” to both questions, McCarthy, who helped write a scientific formula and a paper regarding the risk analysis of fans attending sporting events, advised that risks had little to do with whether fans were masked or socially distanced.

Rather, undertaking a mathematical, computational risk analysis, McCarthy advised “if vaccines or negative COVID-19 tests are required for attendees, 100% attendance is safe … without requiring vaccinations or testing, it’s not.

“There should be a pass system, like the Coronapas in Denmark: Either a person is vaccinated or has been tested in the previous 72 hours. With such a pass system, we could go back to nearly normal life” at outdoor and even indoor live events, McCarthy noted, adding “if they don’t, I think it’s crazy to fully open.”

McCarthy was part of a team of scientists consulted earlier in May by PGA Championship officials and consulted over the past pandemic year-plus by more than 30 teams, leagues, states and cities across the country and the four major U.S. professional sports.

McCarthy wrote the model, published in the journal PLOS ONE in January this year, along with Barry D. Dewitt at Carnegie Mellon University, Bob A. Dumas at Omnium LLC and Myles T. McCarthy at the University of Illinois at Urbana-Champaign.

The model estimates the relative infection risks. Such risks and infection numbers have been dropping through the first quarter of 2021 during a nationwide vaccination movement, yet still a sizable portion of adults in the USA remain unvaccinated.

At the same time, the National Hockey League (NHL) and NBA have been allowing fans back through their turnstiles for the playoffs, with some 15,000+ attending New York Knicks games, where McCarthy pointed out they used the state’s Excelsior pass system.

NFL and many college football officials have pledged to return to 100% attendance as of the (Northern Hemisphere) autumn, meaning as many as 100,000 people will be gathering in extremely close proximity, eating and drinking (mask-free).

McCarthy, the Spencer T. Olin Professor of Mathematics in Arts and Sciences and Chair of the Department of Mathematics and Statistics, feels the country is not ready for this according to the numbers already vaccinated.

He advises that vaccinated fans in the stands have “two shields” working in their favour, noting “they have their own vaccination, and they have a very low chance of being exposed to infection from those around them

“So, we’re not going to get a super spreader event.”

However, risk remains with McCarthy citing that heading into Indy 500 weekend, barely one in three Indiana residents were vaccinated - overall, roughly half of all US adults are vaccinated.

He advises “50% vaccination, that’s not a good idea.

“This summer, a baseball game with half the people unvaccinated would be even more dangerous than 50% attendance last summer.”

With the model for the risk analysis included consideration for masking, social distancing, every-day protocols enacted early in the pandemic, he adds “they likely would not be wearing masks as routinely. The people who are vaccinated, they’re going to be exposed to a lot of unvaccinated people. You have one shield [in the form of the vaccine], which is not perfect. The two shields together, with the people around you being vaccinated or tested, is pretty close to perfect.

“I think it is irresponsible to open large events to 100% occupancy without either testing or vaccinating. Especially now with both of those being easy.”

McCarthy continues “the risk depends on the infection rate in the community, which fluctuates.

“As the rate goes up and down, the risk goes up and down. Whatever the given day, you can factor in our model the number of people vaccinated and hence relative risk … so you can come up with a risk plan on any given day. But it’s going to change from day to day.

“As the number of vaccinations in a community goes up, the overall infection rate goes down, so even unvaccinated people pose less of a risk.”

Until the numbers of vaccinated people considerably outweigh the unvaccinated, and the rates of infection, hospitalisations and deaths dwindle to minuscule numbers, there still will be human factors involved: masking, distancing, hygiene to prevent potential infection and guarding against droplet spread.

The PGA Championship that concluded 23rd May - with Phil Mickelson becoming, at aged 50, its oldest winner ever - posed additional challenges for McCarthy and team when consulted by organisers.

Fans would ride a far distance from their parking lots in commuter buses and pop into numerous hospitality tents. To combat those issues, Omnium and the team advised officials to monitor density, require distancing in seating and ensure optimal air flow.

On the topic of air flow, indoor events such as the NBA or NHL playoffs are less of a risk in an arena with a modern, quality ventilation system, he noted, adding “the devil, indeed is in the details.”

Such detail includes the scene near the end of this year’s PGA Championship, when a throng of pre-screened fans crowded around Mickelson.

In one image, there are 160-plus people within 10 metres of the victor - of the one-third whose faces can be made out, only five masks are visible.

Attendance for the Indy 500 represented only 40% of the IMS’ total official capacity of 300,000, with as many as 350,000 fans having turned up in recent years.

Images: The Indianapolis Motor Speedway (top, credit Pixabay), John E. McCarthy of Washington University in St. Louis, USA (middle) and a COVID-19 vaccination (below).