Experts say serology tests unreliable, as immunity doesn’t require antibodies

Infectious disease chief advising Health Ministry warns against using serology tests in rollout of ‘green passport,’ since body fights reinfection even after antibodies fade

A lab assistant holds a blood sample to be tested for COVID-19 antibodies, April 28, 2020, in Houston, Texas. (AP Photo/David J. Phillip)
A lab assistant holds a blood sample to be tested for COVID-19 antibodies, April 28, 2020, in Houston, Texas. (AP Photo/David J. Phillip)

A professional opinion submitted to the Health Ministry has recommended against using COVID-19 antibody tests to determine whether a person is immune to the coronavirus, saying the tool isn’t reliable enough to determine who is eligible to get a “green passport” that grants exemptions from certain restrictions.

Serology tests, which detect antibodies in the blood of people who have recovered from the disease or been vaccinated, have previously been touted by coronavirus czar Nachman Ash as a key method to determine who is less likely to be infected or transmit the virus.

But Tal Brosh, head of the Infectious Disease Unit at Assuta Medical Center in Ashdod and a member of a committee advising the Health Ministry, has filed a document warning that “according to the data known today, serology tests are not a reliable or valid tool to determine the level of protection against infection, neither after recovery nor after getting a vaccine.”

“Therefore, is it not advised to use those tests to follow up on those who received a vaccine, except for medical research,” Brosh and his team wrote, according to Hebrew media reports Wednesday.

The experts based their opinion on recent studies showing that while COVID-19 antibodies generally fade within four to eight months, the body still remains immune to reinfection in the vast majority of cases, meaning the level of antibodies doesn’t accurately predict whether or to what extent a person is immune.

Illustrative: Red blood cells alongside antibodies in an artery. (urfinguss; iStock by Getty Images)

“We have no data indicating that antibody levels as tested by various kits by commercial firms differentiate between recovered people who are immune and those who aren’t,” Brosh’s document says, recommending against using them for any policy decisions.

Israel has already conducted several antibody surveys as a statistical tool to determine whether the country is approaching herd immunity. The recent studies cast a heavy doubt over the validity of the tests even for statistical purposes, since many people who are immune to COVID-19 would show up as negative.

If the new opinion is accepted by the Health Ministry, antibody tests will not be part of the rollout of the “green passport.”

Speaking with Channel 12 news, Brosh accused the companies behind the serology tests of “misleading the public.”

“These tests have some significance, but right now we have no confirmed data enabling us to rely on their results to determine if a certain person is immune to COVID-19,” he said. “This craze of running to serology tests to see if the vaccine works or if an individual has recovered is completely baseless and shouldn’t be done.”

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