Reports from Asia had caused a sensation in the past few days: Already cured patients should test positive again for the coronavirus have been. In South Korea, according to the authorities, 91 people recovering from a coronavirus infection had the disease Covid-19 again. The director of the Korean Center for Disease Control KCDC, Joeng Eun-kyeong, said that the virus was more likely to have been “reactivated”.
So is it possible that these people weren’t immune after all? Can you catch the virus twice?
The World Health Organization (WHO) can’t say for sure if that Presence of antibodies gives complete protection against a second disease. “We don’t know,” said WHO emergency director Mike Ryan, who directs the global fight against the virus. “We can only draw conclusions from our knowledge of other corona viruses, and even with them, our data are limited.”
Early research indicated that only a small proportion of the population had such antibodies, said Mike Ryan. This also speaks against the development of a so-called herd immunity. Therefore, it “may not solve the problem of the government”. With herd immunity, such a large part of the population is immune to a disease that the relevant pathogen can hardly spread.
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However, epidemiologists hope that an infected patient will recover after recovery immune for at least a few months is. “Being immune means that the body has developed a defense reaction against a virus. And because this immune reaction has a ‘memory’, it means that it will later prevent infection with the same virus, ”explains immunologist Eric Vivier from the University Hospital in Marseille.
In general, it takes around three weeks for RNA viruses, which include Sars-CoV-2 in addition to the newer influenza pathogens, to produce enough protective antibodies, says Vivier. Experience has shown that this protection lasts for several months.
When almost 800 people died worldwide during the Sars epidemic from November 2003 to summer 2003, the patients were “protected for an average of two to three years after their recovery,” explains François Balloux, an expert from London University College. “So you can get infected again, but the question is: after what time?” He adds: “We’ll only know that afterwards.”
A recent Chinese study with rhesus monkeys gives hope: Accordingly, the animals infected with the virus became resistant a few weeks after their recovery. According to Frédéric Tangyn from the Paris research center Institut Pasteur, the study says nothing about the period of an immunity – because it only lasted one month.
Background information about the corona virus:
However, many experts are skeptical about the reports from Asia that coronavirus patients contracted a second infection. They think it is rather unlikely that it is actually a new infection.
According to Balloux, the virus could affect some people become chronic, such as the herpes pathogen. Or the negative Test results are incorrect and in reality the patients never got rid of the virus: “That would indicate that people remain contagious for long periods, several weeks,” he says. “That would not be ideal.”
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A study published in early April with 175 cured Shanghai patients showed that most of them had developed different concentrations of Covid-19 antibodies between ten and 15 days after the onset of the lung disease caused by the virus. But whether “the presence of antibodies can be equated with immunity alone is another question,” warns the US expert at the WHO, Maria Van Kerkhove.
“We wonder if someone who had Covid-19 is really that much protected,” says virologist Jean-François Delfraissy, who advises the French government. Even worse: According to Pasteur researcher Tangy, the antibodies could even aggravate the disease. He points out that the worst symptoms of Covid 19 do not appear until a patient has already developed antibodies.
It is also unclear who develops more effective antibodies – the most or the least affected patients, the elderly or the young? For Australian epidemiologist Archie Clements, only one thing is certain: “The only real solution is a vaccine.” (AFP / Reuters)