COVID-19 ‘immunity passport’ won’t work for now -WHO
April 27, 2020
THE World Health Organisation has said that there is currently no evidence that people who have recovered from COVID-19 and have antibodies would be protected from a second infection.
A WHO guidance said: “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.
“At this point in the pandemic, there is not enough evidence about the effectiveness of antibody-mediated immunity to guarantee the accuracy of an ‘immunity passport’ or ‘risk-free certificate’.
“People who assume that they are immune to a second infection because they have received a positive test result may ignore public health advice.
“The use of such certificates may therefore increase the risks of continued transmission,” the UN agency added.
The WHO guidance explained: “The development of immunity to a pathogen through natural infection is a multi-step process that typically 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 virus and may even prevent it from causing symptoms.
“This non-specific response is followed by an adaptive response where the body makes antibodies that specifically bind to the virus.”
The statement went on: “These antibodies are proteins called immunoglobulins.
“The body also makes T-cells that recognise and eliminate other cells infected with the virus. “This is called cellular immunity.
“This combined adaptive response 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.”
The WHO said it supported many countries that were now testing for SARS-CoV-2 antibodies among health workers, close contacts of known cases, or within households.
It said these studies were critical for understanding the extent of – and risk factors associated with – infection.
“These studies will provide data on the percentage of people with detectable COVID-19 antibodies, but most are not designed to determine whether those people are immune to secondary infections,” the WHO noted.
The guidance added: “Laboratory tests that detect antibodies to SARS-CoV-2 in people, including rapid immunodiagnostic tests, need further validation to determine their accuracy and reliability.
“Inaccurate immunodiagnostic tests may falsely categorise people in two ways.
“The first is that they may falsely label people who have been infected as negative, and the second is that people who have not been infected are falsely labelled as positive.
“Both errors have serious consequences and will affect control efforts.”
The guidance went on: “These tests also need to accurately distinguish between past infections from SARS-CoV-2 and those caused by the known set of six human coronaviruses. “Four of these viruses cause the common cold and circulate widely.
“The remaining two are the viruses that cause Middle East Respiratory Syndrome and Severe Acute Respiratory Syndrome.
“People infected by any one of these viruses may produce antibodies that cross-react with antibodies produced in response to infection with SARS-CoV-2.”