Illustration: Sarah Grillo/Axios

Health care workers and those in other front-line, highly vulnerable sectors will likely benefit the most as new tests come on the market to determine whether a person has had the coronavirus.

The big picture: Serological testing, along with diagnostic testing and contact tracing, is one of the basic tools public health experts say are key to managing the pandemic.

Serological tests identify the antibodies a patient's body produces when it fights this strain of the coronavirus. They test for past infections, not current ones.

  • Some people likely contracted the coronavirus but didn't feel sick, or weren't able to get a diagnostic test. Serology tests will confirm whether they had it. And on a larger scale that will provide more information about where the virus spread, the real number of cases and the actual death rate from the virus.

Yes, but: “People just think this is the solution, that this is finally the thing, that everybody is going to have immunity passports … and I am very skeptical of this for a variety of reasons,” said Ashish Jha, professor of global health at the Harvard T.H. Chan School of Public Health.

  • “It’s going to have limited utility outside of hotspot cities and outside of professions where you’re going to see higher exposure,” former Food and Drug Administration Commissioner Scott Gottlieb told me.

Between the lines: Enthusiasm for serology tests as a way to help get people back to work is rooted in the belief that if you have antibodies for the virus in your system, you're immune from catching it again.

  • But we don't actually know whether that's true, or how strong that immunity might be.
  • And though the basic science is well-established, some officials, including Anthony Fauci, have cautioned the new tests haven’t yet been proven to work well.

Serology testing will be most useful in hotspots like New York City, Detroit, New Orleans, and Miami — areas where a larger percentage of the population has been infected.

  • And if the antibodies these tests detect do end up conferring immunity, the tests will be primarily helpful for workers who are at a particularly high risk of spreading the virus — including health care workers, first responders, grocery store workers and people who work with the elderly.
  • But “outside of the hotspots, I think that the overall rate of positivity is going to be sufficiently low that it’s not going to be a useful tool to return to work,” Gottlieb said.

The bottom line: The value here is in understanding the virus' true spread and helping the highest-risk workplaces operate more safely — not as any kind of universal, nationwide get-back-to-normal permit.

Go deeper: The next coronavirus test we need

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