“We cannot predict how long immunity to this virus will stand,” Prof. Ronit Sarid explained. “But from what we know about other viruses, it will be at least several months or a year.”
By MAAYAN JAFFE-HOFFMANHealthcare workers wheel the bodies of deceased people from the Wyckoff Heights Medical Center during the outbreak of the coronavirus disease (COVID-19) in the Brooklyn borough of New York City, New York, U.S., April 4, 2020(photo credit: REUTERS)
South Korea reported that as many as 116 people have been “reinfected” with the novel coronavirus. Prime Minister Benjamin Netanyahu warned there was “new information coming out” of the Asian country that COVID-19 could be reactivated in recovered patients.Can a person get coronavirus twice?“Reinfection is very unlikely to occur,” said Prof. Ronit Sarid, an expert in virology at Bar-Ilan University. “I cannot accept it. We don’t know any virus that causes reinfection within a month or two after the first infection.”Sarid said there are two possibilities for what we are seeing in South Korea - or what Israel saw in February when one of the Israeli passengers who returned from quarantine in Japan after having been presumed recovered tested positive on arrival in Israel. The first is that certain people carry the virus for long periods, called a “persistent infection.” The second is that sometimes a percentage of SARS-CoV-2 tests could render a false negative or positive.There are seven types of coronaviruses that scientists know humans can contract and SARS-CoV-2 - the official name for the novel coronavirus - is one of them. Sarid explained that of the coronaviruses before this one, four of them cause mild respiratory syndromes and two of them - Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) - may cause more severe syndromes. The four that cause mild diseases do not induce long-lasting immunity. But those infected with SARS or MERS have developed immunity that lasts at least several years.“We cannot predict how long immunity to this virus will stand,” Sarid explained. “But from what we know about other viruses, it will be at least several months or a year.”Prof. Cyrille Cohen, vice dean of the Faculty of Life Sciences at Bar-Ilan University and head of the laboratory of immunotherapy, said this is not only true for coronaviruses but most viruses: if people are infected they generate antibodies that protect them from further infection.“There is no reason to believe that immune memory is not efective against coronavirus,” he said.Though he admitted that there are exceptions - “but even these are not really exceptions.”Take chickenpox. We know that if people get vaccinated for chickenpox they can still develop the disease, although there is just a small chance.
“All of my kids were vaccinated and one of them got a light form of chickenpox,” Cohen told The Jerusalem Post. “Immunization does not always work. We also know people who got sick with chickenpox twice. But if you look at the whole population, it is safe to say most people only get chickenpox once.”The other way a person could become reinfected is if the virus mutates quickly.“With the flu, we need a new vaccine every year,” Cohen explained. “That’s because there are tens of strains of flu and every year we prepare the vaccine by predicting what strains are going to hit us this year.”He said if coronavirus mutates quickly, people could be at risk of reinfection because they would be infected with a different strain of the disease. However, right now, the level of mutation is not that high if one looks at the worldwide population and compares the strains in different countries or individuals.“We see that they are more or less the same,” he said. “The question is how long will it stay the same or will the virus mutate in the future - we cannot always predict that.” And he said that even if the virus does not mutate, we still don’t know over which period of time our antibodies will be effective against the same strain.Still, he said that if one takes into account that worldwide there are several million tests being done, even if there is a small percentage of false negative or positive that amounts to several thousand, that is likely all we are seeing.Most tests are not checking for evidence of antibodies, but the presence of the genetic material of the virus, which is done using a technique called PCR.“It could be that in some cases the test missed,” he said. “We have to take into account that the pathology of this virus is a bit weird. We see people feel OK in the first week of infection, maybe a mild fever, and then get to an intersection and either they recover or suddenly they crash. We also see a lot of symptoms that are new, like loss of smell and taste.“I would say the way the virus behaves is very puzzling in certain patients,” he continued. “The virus might be playing hide and seek for some people.”The way to determine if immunity has been built against coronavirus is by taking a serological test, which identifies if antibodies have been formed to fight it. When a person is infected with the virus, the virus induces the production of these antibodies to inhibit infection, Sarid said. By the time the body has finished fighting the virus, it has developed improved antibodies that should be 10 to 100 times more performant than even the first round - and those are the one that last.The serological test will show both the early stage and late stage antibodies.Sarid said that currently there are several tests that were developed and are commercially available to serologically test for SARS-CoV-2, but until now they have not been properly validated. In Israel, she continued, there are teams reviewing the tests and they should be available within days.Cohen said he, too, is aware that the tests are meant to be rolled out soon and that they will be used alongside the PCR test, which together can give Israel a clear picture of how much and how fast the virus has spread.“I don't know to whom or what frequency, but serological tests will be a major part of our exit strategy,” he said.The serological tests will also help validate the concept of herd immunity, that the disease will eventually become eradicated by infecting a large segment of the population who then becomes immune to it. A concept that Oren Kobiler, a virology specialist in Sackler Faculty of Medicine at Tel Aviv University, said sounds good but is really “a very big question mark.”“We don’t actually know how many people had the virus before in Israel or the world,” Kobiler said. “There is no real evidence that antibodies correlate to protection against this virus. But until we have protection, such a vaccine, this is the best and simplest idea.”
