The World Health Organisation (WHO) has said that there is no proof to support the belief that people who have recovered from the coronavirus disease are immune to the virus and are not likely contract it again.
Speaking at a press conference in Geneva, an American infectious disease epidemiologist, who works for WHO, Dr Maria van Kerkhove, said, “There are a lot of countries that are suggesting using rapid diagnostic serological tests to be able to capture what they think will be a measure of immunity.
“Right now, we have no evidence that the use of a serological test can show that an individual has immunity or is protected from re-infection.
“These antibody tests will be able to measure that level of seroprevalence – that level of antibodies. But that does not mean that somebody with antibodies means that they are immune,” she said.
She added that it was “a good thing” that so many tests were being developed, but cautioned, “We need to ensure that they are validated so that we know what they say they attempt to measure they are actually measuring.”
Kerkhove’s colleague, Dr Michael Ryan, said the antibody tests also raised ethical questions.
“There are serious ethical issues around the use of such an approach and we need to address it very carefully, we also need to look at the length of protection that antibodies might give,” Ryan said.
“You might have someone who believes they are seropositive (have been infected) and protected in a situation where they may be exposed and, in fact, they are susceptible to the disease.”
Other experts agreed with them. Associate Professor in Cellular Microbiology, University of Reading, Dr Simon Clarke, said, “I agree with Dr Maria van Kerkhove from the WHO. The overconfident assertion by some that having antibodies to the coronavirus causing COVID-19 gives immunity, has been made without any evidence and by some people who should know better. It is reasonable to assume that, as someone recovers from the infection, the immunity they generate will persist for some time, maybe weeks, months or years, but nobody actually knows. We simply don’t yet know what would make someone immune to COVID-19 or whether long-term immunity is even possible.”
Visiting Professor in Medical Virology, Imperial College London, Professor Richard Tedder, said, “When someone has been infected with the COVID-19 virus, there is an immunological response to the virus, which includes the production of antibody. It is correct to say that we are not certain that the presence of this recovery antibody will necessarily protect the person against re-infection. There are a number of reasons for this uncertainty.
“Firstly, it has proved very difficult to produce an antibody test which is both sensitive enough to detect antibody in all recovered patients and of sufficient accuracy not to generate false-positive results. Globally there has been an immense amount of work in developing a range of antibody tests some of which are excellent and some of which are not. In addition, the level of the antibody in the recovered person varies quite widely with a number of studies showing that mild infections are associated with a lower antibody response in recovery.
“Secondly, there are reports of re-infection, but whether these instances are re-infections as such or the persistence of shedding of the virus at low level in the recovery period remains to be defined.”
American television outlet, CNN, also reported a similar finding. It said, “In South Korea, health officials are trying to solve a mystery: why 163 people who recovered from coronavirus have retested positive, according to the Korea Centre for Disease Control and Prevention (KCDC).”
According to CNN, the same had been recorded in China, where some coronavirus patients tested positive after seeming to recover, although there are no official figures.
While experts are still studying the reason for this, a Chinese top respiratory expert, Zhong Nanshan, had during a press conference last week said a recovered person could test positive because fragments of the disease remained in their body.
