Countries like the United Kingdom first relied on the theory until backtracking because of the raising death toll.
The World Health Organization is not sure whether the presence of antibodies in blood gives full protection against reinfection with the new coronavirus, Mike Ryan, the WHO’s top emergencies expert, told a briefing on Friday.
Ryan also said that even if antibodies were effective there was little sign that large numbers of people had developed them and were beginning to offer so-called “herd immunity” to the broader population.
“A lot of preliminary information coming to us right now would suggest quite a low percentage of population have seroconverted (to produce antibodies),” he said.
“The expectation that ... the majority in society may have developed antibodies, the general evidence is pointing against that, so it may not solve the problem of governments.”
"Herd immunity," also called "community immunity" or "herd protection," technically means a form of indirect protection from infectious disease that occurs when a large part of a population is vaccinated and becomes immune to infections, thereby protecting vulnerable people such as newborns, seniors and those who are too sick to be vaccinated.
However, some professionals emphasized that the "herd immunity" strategy only works if most people in the population are vaccinated; and as a tactic for fighting a pandemic without any vaccine, it is novel and somewhat alarming.