The World Health Organization announced Friday that the idea that a one-time infection can lead to immunity remains unproven and should not be relied on as a foundation for the next phase of the response to the pandemic, according to NPR.
The agency released a scientific briefing on Friday, stating that there is currently no evidence that people who have recovered from COVID-19, the disease caused by the novel coronavirus, are protected from a second infection.
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"Some governments have suggested that the detection of antibodies to the SARS-CoV-2, the virus that causes COVID-19, could serve as the basis for an 'immunity passport' or 'risk-free certificate' that would enable individuals to travel or to return to work assuming that they are protected against re-infection," the WHO wrote. "There is currently no evidence that people who have recovered from COVID-19 and have antibodies are protected from a second infection."
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According to WHO, the development of immunity to a pathogen through natural infection is a multi-step process that typically takes up to 1-2 weeks. This process includes a combined adaptive response that may clear the virus from the body, and if the response is strong enough, may prevent progression to severe illness or re-infection by the same virus. This process is often measured by the presence of antibodies in blood.
WHO states that they will continue to review evidence on antibody responses to the coronavirus. They also add that most recent studies show that people who have recovered from infection have antibodies to the virus. However, some of these people have very low levels of neutralizing antibodies in their blood, which may suggest that cellular immunity may also be critical for recovery.
“As of 24 April 2020, no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans,” the WHO states.
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