KUALA LUMPUR, April 18 — In a briefing on Friday, the World Health Organisation (WHO) stated that there was currently no evidence to show that patients who have recovered from coronavirus infection and former asymptomatic carriers with antibodies will develop long-term immunity to Covid-19.
Michael Ryan, WHO’s Covid-19 team leader, said so far there was little evidence of the possibility of “herd immunity.”
“A lot of preliminary information that is coming to us right now would suggest quite a low percentage of population have actually seroconverted (to produce antibodies),” he said.
“There’s been an expectation that maybe herd immunity may have been achieved, the majority of people in society may already have developed antibodies.”
“I think the general evidence is pointing against that.. so it may not solve the problem governments are trying to solve.”
Epidemiologist Maria Van Kerkhove emphasised that the presence of antibodies did not mean that a person was no longer at risk from infection.
“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 serologic test can show that an individual is immune or protected from infection,” she said.
“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 also mentioned that guidance on this issue would be provided later in the week.
Ryan also brought up ethical concerns regarding the use of the antibody test.
“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,” he said.
“You might have someone who believes they are seropositive (have been infected) and protected actually in a situation where they may be exposed and in fact they are susceptible to the disease.”
Previously, WHO has said that in most countries, it is too soon to end lockdowns. Ending them prematurely in an attempt to restart economies could result in the reemergence of infections.
There are currently more than 2.2 million cases of Covid-19 worldwide and more than 150,000 people have already died.