COVID tests 2.0: An expert explains the IDF’s wide-scale serological screening

COVID tests 2.0: An expert explains the IDF’s wide-scale serological screening

Immunologist Mordechai Gerlic has started testing soldiers’ blood, convinced it’s the best way to keep them safe from virus during missions

A health worker draws blood from a patient for a COVID-19 antibody test at the Volusia County Fairgrounds in DeLand, Florida, on May 5, 2020. (AP Photo/John Raoux)
A health worker draws blood from a patient for a COVID-19 antibody test at the Volusia County Fairgrounds in DeLand, Florida, on May 5, 2020. (AP Photo/John Raoux)

Israel’s race to conduct large numbers of coronavirus blood tests is intensifying, as the focus expands from civilian clinics to the military in a development that immunologists say could keep army units virus-free.

Blood sample checks known as serological tests provide a way to assess army units before sending them off on missions, said Mordechai Gerlic from Tel Aviv University’s Center for Combating Pandemics, who is conducting widespread testing in the IDF as part of a study that will involve thousands of soldiers.

Gerlic, a professor of clinical microbiology and immunology, said that with the Health Ministry’s blood sample testing for civilians still in its early stages, his project represents one of the most ambitious uses of serological screening in Israel to combat the pandemic.

He said it could allow the army to send units on missions with peace of mind in regards to coronavirus. He suggested that serological tests are more accurate than swab tests, and if all soldiers in a unit test negative, the army can “assume with 98 percent accuracy that they are clear.”

An IDF soldier at a temporary checkpoint in Jerusalem to check Israelis are not violating restrictions meant to contain the coronavirus, April 2, 2020. (Nati Shohat//Flash90)

The Israel military wouldn’t comment specifically on the serological testing when contacted by The Times of Israel, but did confirm its participation in various medical studies that “are part of the IDF’s assistance to national and international efforts to combat the virus,” and it sent a short outline of Gerlic’s project that was written by Tel Aviv University.

Until now Israel, like most of the rest of the world, has mostly used PCR, or swab testing, to check for coronavirus. But interest is growing internationally in serological screening.

This method isn’t expected to replace PCR testing, as it doesn’t reveal whether or not an infected person has recovered, and swabs are still needed to declare them virus-free once they are better. But blood tests are seen as a complementary tool for doctors.

Gerlic and his colleague, Professor Ariel Munitz, began their project last week as the Health Ministry prepared to launch one of the world’s biggest pushes for civilian serological testing, using tens of thousands of tests kits obtained from abroad.

Mordechai Gerlic (sitting) and Ariel Munitz (standing) from Tel Aviv University’s Center for Combating Pandemics (Yoav Biran)

When people go to clinics for blood tests for general health conditions, they will soon be offered a serological COVID-19 test that will tell them if they have been infected at any point. The Health Ministry expects this to provide a picture of how widespread the virus became in Israel during the first wave, which will allow it to plan better for the future.

This transmission electron microscope image shows SARS-CoV-2, the virus that causes COVID-19, isolated from a patient in the US, emerging from the surface of cells cultured in the lab. (NIAID-RML / Wikipedia)

Gerlic is upbeat about whether this will allow people to be declared immune. The ministry, by contrast, is circumspect on the question, still under consideration by the World Health Organization, of whether somebody who receives a positive serological test — meaning they have been infected — will be safe from reinfection once recovered.

In an interview with The Times of Israel, Gerlic said reports that people are getting infected twice, proving there’s no immunity, are “fake news.” The Wall Street Journal just reported that 160 South Koreans have tested positive for coronavirus after recovering, and hospitals in Israel have reported at least two such cases, but Gerlic thinks that such claims are unreliable.

He was confident that serological testing will have significant benefits in speed, cost and accuracy of screening, in planning for future outbreaks, and — as research progresses — in declaring people immune.

You just started screening soldiers. Serological testing tells you whether somebody has antibodies. If they do, this means they are either infected or have been infected in the past. How are you interpreting results?

If everybody in a unit is negative for antibodies you can assume with 98% accuracy that they are clear, and there is no concern about sending them off as a single unit. If you have people who have tested positive by PCR, you can then check to see using serological testing how widely they have spread the infection, and whether the isolation protocol which took place has been effective. If it has been effective, the virus hasn’t spread, then the rest of the unit can carry on operating normally.

Mordechai Gerlic (left) and Ariel Munitz from Tel Aviv University’s Center for Combating Pandemics (courtesy of Tel Aviv University)

Who shows up as having been infected in serological testing?

Everybody who saw the virus [i.e., the virus entered their body], by definition, was infected, and will normally show to have antibodies. Perhaps he or she was asymptomatic but they were still infected, and will show as such.

Why is there so much excitement about serological testing?

It’s more reliable than swab testing, as antibodies stay longer in our bloodstream. In the long term it will be able to tell us if someone has immunity; it won’t be 100%, but it’s the first step to telling if a person has immunity.

MDA staff performing coronavirus swab testing (Photo: Magen David Adom Israel)

We’ll come back to immunity in a moment, but first, how does serological testing compare to swab testing in terms of cost and speed?

I can do 2,500 tests daily in my lab without a problem, which is more than a quarter of the entire number of swab tests conducted nationally in a day. It takes an hour to process tests, but one person can do many in an hour, and that’s without robotics. If we add robotics it’ll be much faster. I estimate the cost could be a third of the cost of a PCR test.

Your logic is that if you see from antibodies someone has been infected already, they have immunity. But the World Health Organization hasn’t reached this conclusion, and there are questions about whether this principle holds.

It’s still a question, and what we can say so far is we know that a person who was infected has antibodies but we don’t know how good they are. However, we hope we’ll be able to conclude after more research there is immunity and say who is immune. We hope we’ll be able to say, for example, perhaps we’ll put this particular doctor, or other personnel, [to work] in the coronavirus ward because he or she has antibodies.

South Korean soldiers wearing protective gear spray disinfectant to help prevent the spread of the COVID-19 coronavirus, at a shopping district in Seoul on March 4, 2020 (Jung Yeon-je / AFP)

Many people say the claim of immunity is cast into doubt by reports of people being infected twice. In your view are they correct?

This is kind of fake news. If you take what’s out there most of the stories of people being reinfected come from South Korea, and the cases are so few that they are statistically insignificant and probably represent mistakes of swab tests. We don’t really know, but from all the results so far there isn’t really evidence of reinfection.

Your hopes for immunity aren’t limited to antibodies. You also expect immune cells known as T cells to stop people from being reinfected. Tell us about that.

A big part of our immunity doesn’t come from antibodies. In lay circles, everyone talks about antibodies, but really a significant part of our immunity comes from specific cells, T cells, and these cells can recognize small fragments of the virus that is normally seen in infected cells. These T cells will usually kill the infected cells and stop a virus.

Liat Edry-Botzer prepares samples for serological testing at the Tel Aviv University lab run by Mordechai Gerlic and Ariel Munitz (Yoav Biran)

As you screen soldiers, there is lots of talk about serological testing for civilians, to help authorities build up a picture of the country. How will this “intelligence” be used?

At the moment we have limited knowledge of how widespread the virus has been, but if serological tests tell us that a high percentage of the population already had the virus and has antibodies, then during a second wave there may be no need to put people into lockdown. What is more, if say, 50% of the people had antibodies, it could mean we have herd immunity. If the opposite is the case, and only a very small percentage of people have encountered the virus, this will shape government policy in the opposite direction.

Can you explain simply how you conduct a serological test?

The machine we use isn’t new. What’s new is that we’ve developed a protocol and worked out which protein to take from the virus for tests. We cover a surface with this protein, and take antibodies from the blood being tested. If there are coronavirus antibodies present, they stick to the protein, and we know that the test result is positive.

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