Dr. Jay Bhattacharya, a professor at Stanford University, cautioned against...

Dr. Jay Bhattacharya, a professor at Stanford University, cautioned against extrapolating the study's data into the general population but that it serves as further data points as research continues all around the globe. Credit: AP/Rod Searcey

Results of a recent study of MLB team employees, including Mets and Yankees, added to the growing body of evidence that the new coronavirus is far more common and therefore far less deadly than initially feared.

Researchers revealed Sunday that 70% of those who tested positive for COVID-19 antibodies — a sign of previous infection — reported no symptoms, bolstering the idea that the disease is more prevalent than one would guess based on those who appear sick.

“It’s sometimes a very deadly disease, but it’s most often asymptomatic or mild, especially in this kind of relatively healthy population,” Dr. Jay Bhattacharya, a Stanford professor who ran the study, said on a conference call with reporters. “What we learned from this study is, nationwide, the range of clinical presentations include a substantial amount of people who are infected with the disease but have very few symptoms and don’t proceed to the viral pneumonia.”

Stanford teamed up with the Sports Medicine Research and Testing Laboratory, an anti-doping company in Utah, to test 5,603 people who work for MLB clubs — some players, but mostly regular employees who work in business and baseball operations.

The study found antibodies in just 0.7% of subjects, about 40 people after researchers accounted for false positive and false negative rates. That was lower than Bhattacharya expected but still seven times the rate of infection based on confirmed COVID-19 cases.

He cautioned against extrapolating the antibody rate to the general population because MLB team employees are not representative of the general population. They all have jobs, for example, and largely can work from or stay at home. And the subjects were mostly working-age adults — 95 percent under 65 — and few reported underlying conditions.

It also means that those who work for MLB teams are generally healthier than others in their communities.

“If this population was social isolating and practicing good PPE [masks, gloves, etc.], then it shows that that works,” said Daniel Eichner, SMRTL president. “That means if that works well, they have to keep doing it.”

The researchers noted that this study’s origin and results have nothing to do with MLB’s effort to stage a 2020 season. It was a public health study that happened to use people who work in sports, after MLB — approached by the researchers — volunteered its workforce.

They used at-home, self-administered antibody tests mailed to willing subjects at their homes and used April 14-15. Those tests are different from the type used by health-care professionals trying to identify active cases of COVID-19, the disease caused by the new coronavirus.

Bhattacharya plans to send a paper on the study to a peer-reviewed journal, but he discussed the findings publicly first because of the “incredible national interest” he received, he said.

The finding that most antibody-positive participants were asymptomatic, suggesting a lower degree of danger than initially believed, aligns with results of recent similar studies.

In New York, the domestic epicenter of the pandemic, a study conducted by the state found antibodies in about one in five — 20% — of New York City residents. Studies in a pair of California counties, Santa Clara and Los Angeles, found antibody rates of 2.8% and 4.1%, respectively. In all three places, that rate of infection was much higher than previously known.

Far from definitive on its own, the MLB study joins those — as well as future research — as needed data points as the scientific and health-care worlds try to figure out the coronavirus.

“This is a really important peek into the public-health consequences of COVID and also the nature of the disease,” Bhattacharya said.

More MLB news