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What the Coronavirus-Antibody Study of Major League Baseball Tells Us

Scientists work in a lab testing COVID-19 samples at New York City’s health department in New York City, April 23, 2020. (Brendan McDermid/Reuters)
We’re still nowhere close to herd immunity.

A study of nearly 6,000 Major League Baseball employees found that just 0.7 percent tested positive for antibodies present in individuals who have recovered from coronavirus infections.

Important news up front for baseball fans: The study doesn’t really have any bearing on MLB plans to play ball for a partial season beginning later in the summer. On Monday, Major League Baseball owners sent a plan to the MLB players’ union to start a season in July without fans. The ability to pull that off will largely depend on several factors, including mass-testing of players and the players willingness to agree to the plan.

What this study, along with others, does tell us is that most people in the United States remain susceptible to being infected by SARS-Cov-2, the virus that causes the disease COVID-19. In other words, the country isn’t anywhere close to reaching herd immunity.

“In a sense, the epidemic has quite a bit to go. It’s only sort of started in this population,” Dr. Jay Bhattacharya, a professor of medicine at Stanford University, who helped conduct the study, told National Review on Monday. Though the study was conducted of employees in just one industry — including front-office workers, players, concession workers, and others — the survey of 26 MLB teams “provides a peek into the epidemic nationwide,” says Bhattacharya. When accounting for errors in the test, the true percentage of MLB employees with antibodies could range from 0.28 percent to 1.15 percent.

Only a few coronavirus antibody studies have been conducted across the country so far, but each had shown a higher prevalence of earlier coronavirus infections. A University of Miami study found that 6 percent of Miami-Dade County residents had antibodies. About 20 percent of New York City residents have tested positive for antibodies.

In April, Bhattacharya helped conduct a coronavirus-antibody study of Santa Clara County in California that concluded anywhere from 2.5 percent to 4 percent of the county’s residents had recovered from the infection. He said at the time that that number was “nowhere near” the threshold for herd immunity, although he cautions that when discussing herd immunity it is important to note that we don’t even know how long immunity lasts for those who have coronavirus antibodies.

If herd immunity to the SARS-Cov-2 virus is possible, at what point would it be achieved? “Let’s say there’s a component of folks who are sort of naturally immune for whatever reason that we don’t understand. Well, then herd immunity would be a lower number,” Bhattacharya said last month. “If that’s not true, you need, you know, 70 to 80 percent [of the population infected]. That could happen.” Harvard epidemiology professor Marc Lipsitch recently told National Review the herd-immunity threshold for the new coronavirus could be anywhere from 35 percent to 75 percent of the population.

Other coronavirus antibody studies have been used to get a better understanding of what the infection-fatality rate is for the coronavirus. As Bloomberg columnist Justin Fox wrote in an April column, the initial round of studies indicate the death rate could be anywhere from 0.12 percent to 1.08 percent. The study of Major League Baseball doesn’t really shed any light on the fatality rate because only 60 people in the study tested positive for coronavirus antibodies, and no MLB employee is believed to have died of COVID-19. The study was conducted of largely working-age people, and so finding zero fatalities out of sixty positive cases is not surprising.

What was unexpected was finding that only 0.7 percent of MLB employees have been infected throughout the country.”I was surprised by it,” says Battacharya. “I was expecting it to be a little higher.”

Up next for Bhattacharya’s coronavirus research is an antibody study of residents of Mumbai, India, where more surprises may await.

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