The jury is still out. Scientists say permenant cure from Covid-19 is a big ask as of now. It depends on how the pathogen transforms inside the body and how the overall defence mechanism is built
Last month, a man who recovered from Covid-19 in Himachal Pradesh tested positive again after a few days. In South Korea, about 180 Covid-recovered patients tested positive again, raising fears — especially among health experts and policymakers — whether the novel coronavirus could infect a person twice.
Usually, the human body develops some immunity against the pathogen once it recovers. But the quantum of immunity depends on the pathogen the body fights. Once an individual recovers from an infection, the immune system blocks further infection by producing antibodies, which will fight the pathogen. In the case of diseases like measles, the body develops lifelong immunity. But in influenza, the virus keeps mutating. So, even if the immune system develops antibodies, a new strain of the virus can break the defence and cause infection. In the case of SARS, the immunity lasts for a couple of years.
In the case of Covid-19 also, scientists and experts believe that the body would develop some immunity. But they are not sure how long the protection would last — a few months, a few years or a lifetime. What gives hope in the fight against Covid-19 is that the coronavirus mutates slower than the influenza virus, in whose case the immunity protection doesn’t last more than six months. In the case of the fast-mutating virus, even vaccines may not work as the virus can always come back with a different strain.
But as the coronavirus doesn’t mutate radically, scientists believe that the general immunity could be longer and vaccines might offer lasting protection. SARS-CoV-2, the virus that causes Covid-19, mutates fewer than 25 times a year, compared with influenza’s mutation rate of almost 50, according to computational biologists at Nextstrain, an open source project tracking viruses. Even if the infection comes back, it might be milder than the first, say the researchers. Last month Martin Hibberd, a specialist in emerging infectious diseases at the London School of Hygiene and Tropical Medicine, told The Wall Street Journal that a protective response to SARS-CoV-2 will last somewhere between six months and 60 years.
Scientists have reached a conclusion that the immune system develops protection, once the patient is recovered, against the same strain of infection. In March, a group of Chinese researchers infected four rhesus macaques — a species of Old World monkeys — with new coronavirus. After their recovery, they tried to reinfect two of them with the same strain. But the macaques did not fall ill again.
If the recovery offers some kind of protection, then why did recovered patients test positive? Researchers believe that’s because of false-negative test results. A healthy body could start developing antibodies within a few days of infection, beginning to fight the virus back. But how long it actually takes for cure depends on the patient. In some cases it takes weeks. For example, a 62-year-old asymptomatic woman in Kerala tested positive 19 times before she was finally declared recovered. Researchers say in the later stage of the infection, the virus could retreat to lungs where it can delude detection, and then strike back. That’s one possibility for hundreds of South Koreans having tested positive after negative results. Another explanation says dead fragments of the virus stay in some patients’ bodies, which could show positive results. It doesn’t necessarily mean that the patient is sick again.
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