So far no evidence has been found that can confirm that serological tests can objectively indicate that an individual has acquired immunity from the novel coronavirus or can no longer be at risk of being reinfected with the virus, warned the World Health Organization on Friday.
“These antibody tests will be able to measure that level of serology presence, that level of antibodies, but that does not mean that somebody with antibodies” is immune, said Dr. Maria Van Kerkhove, head of WHO’s emerging diseases and zoonosis unit.
It is possible to ascertain whether an individual has had Covid-19 in the past and was either asymptomatic or recovered, with the help of the so-called serological, or antibody, tests.
According to data compiled by Johns Hopkins University, more than 560,000 people out of the 2.1 million people infected by the coronavirus have been marked as recovered around the world. But the case total is likely much higher because many people have remained undetected and because many countries have not been able to test enough number of people for the virus infection, infectious disease experts say.
The US has just started to implement antibody tests. States in the country that are now planning to open up economic activities and relaxing some of the strict social distancing measures imposed to combat the pandemic have been advised to use the tests by the US President Donald Trump. The total number of people infected so far in the country is more than 671,000.
Many countries are suggesting that the serological tests would be able to “capture what they think will be a measure of immunity”, WHO officials discovered, Kerkhove said.
“What the use of these tests will do will measure the level of antibodies. It’s a response that the body has a week or two later after they’ve been infected with this virus,” she said at a news conference at WHO’s Geneva headquarters.
“Right now, we have no evidence that the use of a serological test can show that an individual is immune or protected from reinfection,” she added.
The length of protection the antibodies could give to people who have been infected by the coronavirus and have recovered is still being determined by scientists, said Dr. Mike Ryan, executive director of WHO’s emergencies program.
“Nobody is sure whether someone with antibodies is fully protected against having the disease or being exposed again,” he said. “Plus some of the tests have issues with sensitivity,” he added. “They may give a false negative result.”
Al of the people who manage to recover from the coronavirus infection had the antibodies to fight a second infection, said WHO officials earlier this week. That raised concerns that immunity may not be developed by people who recover from the coronavirus infection.
“With regards to recovery and then reinfection, I believe we do not have the answers to that. That is an unknown,” Ryan said Monday.
(Adapted from CNBC.com)