E-Paper
WHO warns against ‘immunity passports’ as nations look for ways to exit lockdowns
The WHO does not have a position on this approach and the scientific brief will be updated as new evidence emerges, so countries must tread with caution, said the global health agency’s South East Asia regional director.
The World Health Organization (WHO) on Saturday warned governments against issuing “immunity passports” or “risk-free certificates” to people who have recovered to enable travel or return to work because there is no evidence that people who have recovered are protected from a second infection.
Chile said it would start issuing immunity cards to people who have recovered from Covid-19, and the US , Germany and Italy are considering it as a way to exit their lockdowns.
The assumption is that a person who has been infected and has recovered can safely interact with people without getting reinfected or infecting others.
The WHO’s scientific paper warns that the assumption that those who have recovered are protected from reinfection could fuel continued spread of Covid-19 as people with certificates may stop taking standard precautions, such as wearing masks and washing hands.
“Some governments have suggested that the detection of antibodies to the SARS-CoV-2 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 reinfection. There is currently no evidence that people who have recovered from Covid-19 and have antibodies are protected from a second infection,” the scientific brief said.
The WHO does not have a position on this approach and the scientific brief will be updated as new evidence emerges, so countries must tread with caution, said the global health agency’s South East Asia regional director.
“Right now, we have no evidence that a serological test can show that an individual is immune to Covid-19. Also, we need to be sure what test will be used to establish the status of an individual. Preliminary information received suggests that a very low proportion of the population has developed antibody response to Covid-19. So this approach may not solve the problem governments are trying to address,” said Dr Poonam Khetrapal Singh, WHO regional director, South East Asia Region.
A rising concern is the unreliability of antibody tests, which can throw up false positive and false negative results. “Antibody tests, while suggestive of a person’s exposure to the Covid19 virus, do not provide proof of full immunity, which is protective to that person or impunity from being regarded as infective to others. If applied on a large scale at the population level, false positives tend to get magnified,” said Dr Srinath Reddy, president, Public Health Foundation of India.
While people who have recovered from the infection have antibodies against the virus, some of them have very low levels of neutralising antibodies in their blood, “suggesting that cellular immunity may also be critical for recovery”, the WHO paper says.
The development of immunity to a virus through natural infection is a multi-step process that takes place over one to two weeks. The body responds to a viral infection immediately with a non-specific innate response in which macrophages, neutrophils, and dendritic cells slow the progress of the virus and may even prevent it from causing symptoms. This non-specific response is followed by an adaptive response, where the body makes antibodies called immunoglobulins that specifically bind to the virus.
The body also develops cellular immunity by making T-cells to eliminate other cells infected with the virus. This (cellular immunity) combined adaptive response may clear the virus from the body, and if the response is strong enough, may prevent progression to severe illness or reinfection by the same virus. This process is often measured by the presence of antibodies in blood.
“As of April 24, no study has evaluated whether the presence of antibodies to SARS-CoV-2 confers immunity to subsequent infection by this virus in humans,” said the WHO paper.
