Herd immunity, or great second wave? Antibody tests in Israel hope to discover
JERUSALEM: Israel, whose aggressive response to it has kept its death rate at a fraction of that of the United States and other affected nations, is preparing a national serological test of 100,000 citizens to see how widespread the virus has spread in its population and how vulnerable it can be to a new wave of contagion.
The survey, which will be conducted in Israeli HMO-run clinics starting in one or two weeks, is one of the biggest efforts to determine the prevalence of antibodies against Covid-19. Germany has also announced antibody tests using a nationally representative sample.
The results could help decide how quickly companies and schools should be allowed to return to normal operations. On Monday, Israel announced that citizens could leave their homes after a 40-day blockade, but many aspects of economic and social life remain restricted.
Even more important, authorities said, the survey results could spur preparations for any strong resurgence of the virus, perhaps when hospitals and health clinics are also busy with seasonal influenza.
This is the most important mission: get ready for the next wave, especially a wave during the winter, Moshe Bar-Siman-Tov, director general of the Israel Ministry of Health, said in an interview on Tuesday. Fortunately, Covid-19 caught us after the flu season. But we cannot assume that there will not be a next wave or that it will be during the summer.
Authorities say they hope the survey will identify the portion of the healthy population that has not yet been exposed to the virus, and the portion that has already been exposed but has developed antibodies against the virus. The answers could have huge implications for a country's ability to resist a new wave of the virus.
If antibody testing shows that a sizable portion of the population has developed antibodies, that could mean Israel is on the path to collective immunity and would be well equipped to resist further outbreaks.
But if tests show that only a small percentage of the population has been exposed, the country's health system could still be overwhelmed by the spread of Covid-19, Bar-Siman-Tov said. He said estimates of the percentage of Israelis with antibodies vary widely, from less than 1% to more than 10%.
We want to know the truth, he said.
The World Health Organization warned that there is no evidence that people who have recovered from COVID-19 or who have antibodies are protected from another infection.
But Dr. Yair Schindel, a member of a working group at the Ministry of Health on the virus that pushed for a large survey, said the Israeli study could produce such evidence. Part of what we are trying to achieve here is answering the questions posed by the WHO, he said.
Schindel outlined two scenarios for Israel.
In the pinkest, the survey would show that 10% of Israelis have antibodies against Covid-19. If so, and if a future wave of the virus caused the same proportions of Israelis to become seriously ill or die so far, that would mean that some 2,300 people would need intensive care, Schindel said. That would be within the capacity of the country's health system.
But in a bleaker scenario, the survey would reveal that only 1% of Israelis have antibodies, in which case the number of people needing intensive care beds in a future wave could exceed 12,000, well beyond the capacity of Israel said.
It is an exercise in epidemiology, so critical that it is really important, said Schindel, co-founder of aMoon, an Israeli hedge fund that invests in new life science companies.
Israel spent nearly $ 40 million to obtain 2.4 million antibody tests from two suppliers that they have received from the Food and Drug Administration: Abbott Laboratories in the United States and DiaSorin in Italy.
A potential pitfall: If the coronavirus mutates, blood tests may not be able to identify it, Schindel said. Another is that not all FDA-approved antibody tests have been shown to be reliable.
Blood tests verify in plasma the specific iterations of Immunoglobulin-M, or IgM, and Immunoglobulin-G, or IgG, which are created by the immune system in response to Covid-19. While IgM is created rapidly as part of the body's response to infection and soon dissipates, IgG remains in the body and represents our memory of our immunity, Schindel said.
Patients who visit their clinics for blood tests for ordinary reasons will be asked to allow their samples to also be tested for coronaviruses.
They will also be asked to complete questionnaires about whether they experienced symptoms and when, whether they were isolated at home or hospitalized, who among their friends and family contracted the virus, and so on.
Those whose blood tests show the presence of antibodies against the coronavirus will be called again for a standard polymerase chain reaction, or PCR, test for the virus, to determine the correlation between viral load and antibody levels, Bar said. -Siman-Tov.
There are so many things we can learn and research, if we plan it correctly, he said.
Asking so many citizens to undergo something as invasive as a blood test could seem like a difficult task in a country where a digital surveillance initiative to identify coronavirus patients using smartphone location data sparked protests and political demands. Many Israelis, citing privacy concerns, also refused to download a government-sponsored app that was designed to help them avoid their fellow citizens who tested positive.
But Bar-Siman-Tov said he did not expect the survey to be difficult to sell because participants will be informed of the results. I think people would like to know, he said. I mean, I think of myself and I would like to know. He added: I think we will have more demand than supply.
Furthermore, either because of a tendency to hypochondria or because its socialized health care system makes it cheap and easy, up to 70-80% of Israelis already draw blood in a given year, Bar-Siman-Tov said.
Israelis are addicted to health services, he said, laughing.
In addition to the broad national sample, Bar-Siman-Tov said the ministry planned to evaluate higher concentrations of subjects in cities that have experienced major outbreaks, such as Bnei Brak and Jerusalem. Health workers will also be evaluated in a group. The remaining antibody tests will be made available to researchers for further studies, he said.
If the national survey shows that a large part of the population has obtained immunity, that could prompt the government to ease the remaining restrictions faster, Bar-Siman-Tov said. But he said there was no going back to a stricter blockade based only on serological testing.
Although Israelis have complained about the chaos and inconsistency in how the rules have been developed and enforced, the country has done relatively well, with only 237 deaths and 16,268 cases as of Tuesday afternoon. Deaths per million inhabitants are 27 in Israel, compared to 213 in the United States.
Bar-Siman-Tov said that Israel's experience had shown that being preventive was the key.
The time to take action, or to take the action you want to take during pandemics, is when you think it is too early, he said, recalling the decisions that began with the cancellation of airline flights from China in early February.
Everyone thought we were being too aggressive about it, or just exaggerating the threat, that nothing was going to happen, we were just ruining Israeli foreign affairs, or we were hysterical or ruining the economy, he said. Generally, it took us one day to feel like we did the right thing, and about two or three days for the others.