As the Health Ministry prepares to conduct extensive testing of the population in Israel to get a clearer picture of the infection rate and the number of asymptomatic carriers – by means of throat-swab testing plus 100,000 serological blood tests for antibodies – the professional staff advising the National Security Council is opposing the move.
They argue that this type of testing is unneeded and a waste of precious resources, and that the focus should be on testing patients who show symptoms indicative of the coronavirus and on cutting off the chains of infection.
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In an interview with the New York Times, Health Ministry director-general Moshe Bar Siman Tov said the ministry is planning to conduct serological testing for antibodies on 100,000 Israelis to assess the spread of the virus and prepare for a possible second wave of it.
Professor Eli Waxman, head of the advisory team to the National Security Council, maintains that survey testing on the general population is unwarranted, given their estimation that the rate of virus carriers in Israel is just 0.1 percent.
“The survey testing was pushed by those who say that the number of carriers in the population is much larger than the number of confirmed cases, that it falls between 1-10 percent of the population and needs to be measured,” Waxman said in a lecture this week to Weizmann Institute of Science researchers. He presented figures showing that of the sampling of 5,600 tests taken among asymptomatic workers in the government and security agencies, only five were found to be carriers.
“If the rate of asymptomatic virus carriers is very large, then the testing of symptomatic patients that was done here and in other places in the world is missing most of the patients. If this is the situation, we won’t be able to cut off the chains of infection and the number of carriers in the general public is much larger than what we think, and therefore survey testing should be done, and a policy of going for herd immunity may be possible,” Waxman said.
But this is not the situation, he insisted. In the first report his team submitted to the NSC, on March 18, they said that asymptomatic carriers accounted for fewer than 25 percent of the total number of people infected – in other words, that in at least 75 percent of infections, suspicious symptoms would appear that would lead to testing.
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At the time, the team based its conclusions on the results of testing of all 3,700 passengers on the Diamond Princess cruise ship: Fewer than 20 percent were found to be asymptomatic carriers.
In its analysis, the team also cited the information about the way in which South Korea halted the spread of the pandemic there. “Suppression of the outbreak there was accomplished by cutting off the chains of infection by testing symptomatic patients. If the number of asymptomatic carriers was very large, this strategy would not have worked,” the report argued.
“Today we know with very high certainty that we were right. The March 31 report by the CDC in the United States, the survey testing done in Australia and reported on April 10, the testing of the sailors on the aircraft carrier Roosevelt from April 26 and the De Gaulle from April 19 – all confirm the conclusion that the percentage of asymptomatic carriers is lower than 25 percent,” Waxman says.
‘The models are misleading’
Accordingly, he argues that testing should be focused on patients with symptoms. To illustrate his point, he says that doing 3,000 survey tests in the general public will turn up just three cases, while doing 3,000 tests among patients with suspicious symptoms will turn up 300 cases. Therefore, he says, there is no real value to general survey testing – both because the rate of asymptomatic carriers can be estimated closely and because this doesn’t contribute to cutting off the chains of infection and suppressing the pandemic, and so is a waste of a precious resource.
The approach advocated by the NSC advisory team is completely different than that of the Health Ministry, and of the public health professionals and epidemiological experts who believe survey testing is a vital tool for epidemiological analysis of the COVID-19 infection rate in Israel.
Recently, with the decline in the number of confirmed cases, tests are being diverted more toward survey testing of the general public to get a picture of the rate of carriers of the virus. Over the next two weeks, the Health Ministry is slated to undertake expanded survey testing that will include 100,000 serological blood tests in “red zones” and among workers who come in contact with the public, such as medical personnel and police.
Israel acquired 2.4 million antibody tests at a cost of 110 million shekels ($31.4 million) to aid in the process of returning to the pre-virus routine and see whether herd immunity is attainable. The NSC advisory team argues that an assumption of herd immunity could lead to disaster and a spike in the infection rate, and that testing people with symptoms and cutting off the chains of infection is the way to get through the coronavirus crisis.
The team has also been critical of the reports and refer to scenarios based on modelling – the mathematical statistical tools that forecast what sort of outbreak will occur in different situations based on different variables. Throughout the crisis, various reports based on mathematical models have been issued, including one by the Gertner Institute, the epidemiological research institute under the Health Ministry, which presented various scenarios at the start of the crisis, some of them apocalyptic.
The Health Ministry also relied on a Gertner Institute model regarding the risk of infection and transmission among children in making its recommendations for the gradual reopening of schools. “We relied on analysis of information from around the world and not on models,” Waxman says. “We quickly came to the conclusion that none of the models are sufficiently validated to allow decision-making with the necessary level of assurance.”