A 33-year-old in Hong Kong was diagnosed with COVID-19 for a second time,142 days after first testing positive, revealed a study done by researchers at the Hong Kong university. This case is the first documented case of reinfection in the world, . Interestingly, scientists at Hong Kong university found that the genomic sequence of the virus in both the COVID-19 infections is different.
The man who returned from Spain did not exhibit any symptoms this time around. Earlier, he had developed cough and fever as well as a sore throat. This news of a reinfection comes at a time when sero-surveys across the world are trying to identify the longevity of the neutralizing antibodies (fight a pathogen) and the T cells ( cells that identify a recurring pathogen).
This is not an instance of viral shedding or the remnants of the virus remaining in an infected person's body, said the authors of the study. As the genomic sequence of the virus differs, the person has been reinfected but is asymptomatic. The scientists are trying to find the implications of this finding as it supports the theory that the existing antibodies did stop the virus from having a stronger effect the second time around.
The variations have been found in the spike proteins with 24 nucleotides which includes the D614G variant that is now prevalent around the world. scientists across the world are studying the duration for which antibodies against SARS-CoV-2 are present in an infected person's body.
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The study has been accepted in the journal Clinical Infectious Diseases and is yet to be published.
Herd Immunity Not Enough
On conducting an antibody test, the researchers found that the amount of antibodies against the virus were very low. This has led the researchers to surmise that achieving only herd immunity will not stop the virus from spreading and people from being infected. People that have already been exposed to as well as been diagnosed with COVID-19 should also be vaccinated once a vaccine is approved, say the researchers from Hong Kong University.
Antibody levels from the first and second infection were not compared. During the first episode, the antibodies were assessed on the 10th day. Studies suggest that it takes at least 2-3 weeks for antibodies to be developed and the scientists did not have this sample. They even assumed that the reason for the low antibodies in the second infection was that the antibodies fought against the virus. This was why the infection was milder the second time around.
The scientists believe that SARS-CoV-2 will now act in the same manner as seasonal common cold causing human coronaviruses. Every new infection will be milder, the scientists believe. Further research should be conducted as this is the only documented study so far, the scientists from Hong Kong University said.
What Does The WHO Say?
In its press conference held on Monday, August 23, Maria Van Kerkhove, epidemiological expert at the World Health Organization said that the reinfection should be studied at a population level.
"What we are learning about infection is that people do develop an immune response, and what is not completely clear yet is how strong that immune response is and for how long that immune response lasts," Van Kerkhove said.
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