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A sign outlines social distancing at Van Wilgen's Garden Mart on the Post Road in Milford, Conn. on Thursday, May 7, 2020.

Tests that can determine whether someone has developed antibodies against COVID-19 are becoming more common, but health experts said it’s still unclear whether having antibodies protects against reinfection.

“We don’t want to give people the wrong impression, because we don’t know what this means yet, if you have antibodies,” said Dr. Zane Saul, chief of infectious disease at Bridgeport Hospital.

Antibodies are the proteins the body uses to neutralize an infection. The presence of antibodies against a certain illness typically means a person was sick and recovered from the infection. Sometimes, the presence of antibodies means a person has protection against reinfection. That’s the case with illnesses such as chicken pox, where being infected once usually means a person won’t get it again, Saul said.

But, he said, with other illnesses — such as the flu — the immunity is only temporary. It’s unknown where along the spectrum the COVID-19 antibodies sit.

It’s unlikely that anyone will know how much protection COVID-19 antibodies offer for at least six to nine months, said Dr. Tom Balcezak, chief clinical officer for Yale New Haven Health System.

Tests for COVID-19 antibodies, also called serology tests, involve taking a blood sample, and examining it for the antibodies. According to the Centers for Disease Control and Prevention, “antibody tests should not be used to diagnose someone as being currently sick with COVID-19. To see if you have a current infection, you need a viral test, which checks respiratory samples, such as a swab from inside your nose.”

Saul said Bridgeport Hospital has antibody tests available, but testing isn’t widespread there yet — partly because of the uncertainty surrounding it, and because the hospital is focusing on those with active infections.

“We’re still working on patients and getting them through infection,” Saul said.

Some health organizations have begun wider antibody testing, including Hartford HealthCare’s GoHealth Urgent Care clinics. The chain has 18 clinics in the state, though five are temporarily closed due to the pandemic. The group started offering antibody testing and, as of Thursday night, at least 400 to 500 such tests had been done, said Dr. Eric Walsh, medical director of Hartford’s GoHealth Urgent Care.

He said patients can go on the website, make an appointment and see a provider, who will ask questions and determine whether they’re eligible for an antibody test, a COVID-19 test or both.

Like Saul, Walsh said it’s still unknown how much protection is offered even if a patient tests positive for COVID-19 antibodies. But he said the tests are useful for helping to determine who has had the illness — particularly since so many patients are asymptomatic. They also can provide some degree of comfort to the general public, Walsh said.

“For a lot of people, there’s a peace of mind in knowing they’ve had it before and survived it,” he said.

Antibody tests have become a hot topic locally and nationally. On May 4, the U.S. Food and Drug Administration released a statement, tightening oversight of antibody tests and requiring companies to send data to the FDA proving the accuracy of their product.

The updated guidelines were in response to concerns about inaccurate tests. Late last month, researchers from the University of California at San Francisco and Berkeley found that many test kits delivered false positives.

Officials from Hartford HealthCare and Yale New Haven Health said the tests they’ve used didn’t appear to have any issues. Even so, the experts agreed that there’s still a lot that’s unknown about antibody testing, and what it means to have COVID-19 antibodies.

“Having a test that’s positive now might mean a lot more as we learn more about the virus,” Walsh said.