Testing for Antibodies Crucial to Ending Israel's Coronavirus Crisis, Experts Say

Serological tests would help authorities answer important questions about the virus – most importantly, if herd immunity is possible and if so, how and how long will it take?

Ido Efrati
Ido Efrati
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A policeman speaks to a driver in the closed-off city of Bnei Brak, April 2020.
A policeman speaks to a driver in the closed-off city of Bnei Brak, April 2020.Credit: Meged Gozani
Ido Efrati
Ido Efrati

Though serology tests – blood tests that detect if one has been exposed to a disease – are essential to eventually exiting the coronavirus lockdown, there isn’t yet any reliable serology test that also produces results promptly.

Such a test would let the Health Ministry determine whether a sufficiently large proportion of Israelis have developed antibodies for the virus, which would enable a gradual easing of the lockdown restrictions.

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These tests would identify carriers who don’t show any symptoms, which the swab tests now in use aren’t very effective at doing. They would also help determine the main concentrations of infection and perhaps who has developed immunity from the virus.

In addition, unlike swab tests, serology tests don’t require treatment in the lab, so they can be done more quickly and in larger quantities. However, the tests can’t be used to diagnose the disease.

“To free up the economy, we’ll have to rely on serology tests and symptoms,” the Health Ministry’s deputy director general, Prof. Itamar Grotto, said Sunday during a meeting of the Knesset’s ad hoc coronavirus committee.

But after examining more than 20 kinds of serology tests for coronavirus, the ministry concluded that none of them are both reliable and quick. “There are good tests, but you don’t get the results on the spot,” Grotto explained.

He also stressed that the lockdown won’t be lifted immediately after the week-long Passover holiday, which starts Wednesday evening. “We need to see what Passover does and whether it causes a rise or a decline” in cases of the virus, he said. “And that will take several days.”

Until now, Israel has focused on “flattening the curve” of the infection – monitoring the rise in the number of verified patients, seriously ill patients and patients on respirators – and increasing the number of swab tests used to detect it. But the swab tests don’t provide a reliable picture of the situation, both because they’re effective only within a limited window of time and because they are only 70 to 80 percent reliable.

The number of severely ill patients also isn’t an ideal indicator, because there’s a lag time of two weeks or more between the time people contract the virus and when they show up in hospitals.

Consequently, the existing information can’t answer important questions like how many Israelis actually have the virus, how many carriers don’t show any symptoms, whether that population has any common characteristics, how many infected people have developed antibodies, or defenses, to the disease and what kind, whether coronavirus patients develop immunity to the virus, and if not, how likely they are to be infected again. All this would help answer the most critical question of all: Is it possible to develop herd immunity to the coronavirus, and if so, how, and how long will it take?

Prof. Eyal Leshem, who heads the Center for Travel Medicine and Tropical Diseases at Sheba Medical Center in Tel Hashomer, said serology tests would help determine what proportion of the population has actually been infected and what proportion has recovered. “When the proportion of recovered patients is higher, the risk of an outbreak and the risk to the elderly decreases, and a state of herd immunity develops,” he explained.

Prof. Eran Elinav of the Weizmann Institute of Science said that Israel must either acquire serology tests or develop its own, along with the ability to carry out tens or hundreds of thousands of them. “This is a strategic capability that must be available to the decision makers,” he said.

Swab tests can identify when carriers have stopped being infectious, while serology tests identify whether they have developed immunity. And both are important “in the process of exiting the disease,” he stressed.

Over the weekend, the U.S. Food and Drug Administration issued its first approval for a serological coronavirus test. Cellex, which makes the test, said it provides results within 15 to 20 minutes, but may not be reliable in the first few days after someone contracts the virus, since they may not have started producing antibodies yet. The FDA is currently evaluating serological tests by 50 other manufacturers as well.

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