The World Health Organization is warning that people who have had Covid-19 are not necessarily immune by the presence of antibodies from getting the virus again.
“There is no evidence yet that people who have had Covid-19 will not get a second infection,” WHO said in a scientific brief published on Friday.
It cautions against governments that are considering issuing so-called “immunity passports” to people who have had Covid-19, assuming they are safe to resume normal life.
“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,’ ” WHO said.Dr. Maria Van Kerkhove from WHO has previously said it’s not known whether people who have been exposed to the virus become completely immune.
WHO continues to review the evidence on antibody responses to SARS-CoV-2 infection. Most of these 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,4 suggesting 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.
Many countries are now testing for SARS-CoV-2 antibodies at the population level or in specific groups, such as health workers, close contacts of known cases, or within households.
WHO supports these studies, as they are 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 new WHO brief underscores that stance, and jibeswith other scientific statements about the idea of developing immunity.
By NK AB
