Mass General Study Found 32% of Group Tested in Chelsea Were Found to Have Immunity to COVID-19

Emergency medical technicians disinfect their equipment after delivering a patient to Elmhurst Hospital Center, Saturday, April 4, 2020 in the Queens borough of New York. The new coronavirus causes mild or moderate symptoms for most people, but for some, especially older adults and people with existing health problems, it can cause more severe illness or death. (AP Photo/Mary Altaffer)


The Boston Globe reports that a team of Mass General doctors conducted 200 immunity tests on residents in the city of Chelsea and found that 32% of these individuals tested positive for antibodies linked to COVID-19.

Chelsea has been one of the hardest-hit areas in Massachusetts. The Globe describes Chelsea as a densely populated, working-class city. The article says, “Chelsea covers only about two square miles, across the Mystic River from Boston. For generations, it has attracted new immigrants, and about 65 percent of its residents are Latino. Many live in three-decker houses, where it’s hard for people to isolate themselves. Many work in the hospitality industry and health-related fields, where exposure to the virus is greater. And a lot of them must go to work during the pandemic.”

The doctors said that about half of those tested told them they’d had at least one symptom of the virus in the past four weeks. The others had not. Chelsea has the highest rate of confirmed cases of the Chinese virus. The Globe reports that “at least 39 residents have died from the virus, and 712 had tested positive as of Tuesday, a rate of about 1,900 cases per 100,000 residents, or almost 2 percent.”

Dr. John Iafrate, vice chairman of MGH’s pathology department and the study’s principal investigator, sees the results as both good news and bad news. “The bad news is that there’s a raging epidemic in Chelsea, and many people walking on the street don’t know that they’re carrying the virus and that they may be exposing uninfected individuals in their families.”


“On the good-news side, it suggests that Chelsea has made its way through a good part of the epidemic. They’re probably further along than other towns,” he added.

It is unknown how long immunity lasts.

The city’s manager Thomas Ambrosino, calls Chelsea the epicenter of the crisis in Massachusetts. He told The Globe, “We’ve long thought that the reported numbers are vastly under-counting what the actual infection is,” Those reported numbers are based on positive COVID-19 tests, and we’re all aware that a very, very small percentage of people in Chelsea and everywhere are getting COVID-19 tests.” The good news, said Ambrosino, is that “it’s kind of sobering that 30 percent of a random group of 200 people that are showing no symptoms are, in fact, infected. It’s all the more reason for everyone to be practicing physical distancing.”

Researchers emphasize that these numbers “couldn’t necessarily be extrapolated for the city’s roughly 40,000 residents.” However, they “provided a valuable snapshot of a community that medical experts say is especially vulnerable to COVID-19.”

Former New York Times reporter Alex Berenson, whom I have mentioned numerous times as one who has been following this pandemic closely, points out that Chelsea’s 32% rate of immunity is a total 16 times the rate of people known to have been infected by the virus. He tweeted that Chelsea’s 32% result is beginning to approach herd immunity. He added that “Chelsea is much more like New York City than a lot of other American towns and suburbs – densely packed – and this kind of number could be a precursor of what NYC antibody testing would show.”



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