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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

Go deeper

The Fed isn't the only problem investors are worried about

Illustration: Aïda Amer/Axios

The Federal Reserve will be raising rates, just as the economy is slowing. The markets hate that.

Why it matters: The ugly start to the stock trading year doesn't just reflect Fed-induced agita — investors are also worried about a growth slowdown.

2 hours ago - Health

White House says Obamacare sign-ups hit record

Health and Human Services Secretary Xavier Becerra speaking in the White House in December 2021. Photo: Jim Watson/AFP via Getty Images

The White House said Thursday that a record 14.5 million Americans have signed up for health insurance through Obamacare marketplaces since Nov. 1, including more than 10 million enrollments through HealthCare.gov.

Why it matters: Last year's stimulus bill contained substantial investments in the program, including increased subsidies for people who don't receive health insurance from an employer or through Medicare or Medicaid.

2 hours ago - World

Kremlin says U.S. written responses ignored Russia's main NATO demand

Sergey Lavrov. Photo: Dimitar DilkoffI/AFP via Getty Images

Russian Foreign Minister Sergey Lavrov said Thursday that the United States' written answers to Russia's security demands do not contain a "positive response" to the Kremlin's top priority, which is a freeze on NATO expansion, according to Russian state media.

Why it matters: A spokesperson for the Kremlin stressed that no conclusions will be drawn until Russian President Vladimir Putin has time to analyze the papers, but a lack of movement on Russia's core concerns means the crisis over Ukraine is unlikely to de-escalate.