“Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic,” WHO Director-General Tedros Adhanom Ghebreyesus said at a Monday media briefing. “It is scientifically and ethically problematic.”
In a public health context, herd immunity typically describes a scenario in which a large enough share of the population is vaccinated against a disease to prevent it from spreading widely, thereby providing default protection to a minority of people who have not been vaccinated.
But as there is still no vaccine for the coronavirus, achieving herd immunity in the current environment would require a large number of people to contract the virus, survive covid-19, and then produce sufficient antibodies to provide long-term protection.
While the scientific community has roundly rejected herd immunity the approach, public interest in it has waxed and waned amid pressure to reopen schools and economies.
Last month, President Trump appeared to praise the idea during a town hall in Pennsylvania.
“You’ll develop herd — like a herd mentality,” he said. “It’s going to be — it’s going to be herd developed — and that’s going to happen.”
British Prime Minister Boris Johnson’s government initially expressed interest in the theory before backtracking amid public outcry over the dangers of letting the virus spread. Johnson himself was hospitalized with a severe case of covid-19, which he said could have killed him.
Tedros, noting that there had been “some discussion” about the concept recently, told reporters Monday that allowing people to be exposed to a deadly virus whose effects are still not fully known was “not an option.”
“Most people who are infected with the virus that causes covid-19 develop an immune response within the first few weeks, but we don’t know how strong or lasting that immune response is, or how it differs for different people,” he said.
Though rare, there are multiple documented instances of people being infected for a second time after recovering from covid-19. An 89-year-old woman in the Netherlands died after being infected with the coronavirus for a second time, Dutch news reported Monday.
Antibody studies suggest that less than 10 percent of people in most countries have contracted covid-19, Tedros said, which is nowhere near the majority that would be needed for herd immunity.
With the “vast majority” of the world’s population susceptible, letting the virus spread “means allowing unnecessary infections, suffering and death,” he said.
Just in the last four days, Tedros said Monday, the global coronavirus count has continued to break its daily record for the number of new confirmed infections.
“Many cities and countries are also reporting an increase in hospitalizations and intensive care bed occupancy,” he added.
Tedros has urged governments to pursue comprehensive plans that include widespread testing, social distancing, and other preventive measures, such as face-mask wearing, alongside a global push to develop a vaccine. The WHO is spearheading an effort to distribute coronavirus vaccines equitably once they are available, which Trump declined to join.