THE HEAD OF the World Health Organisation has warned against allowing Covid-19 to spread in the hope of achieving so-called herd immunity, saying to do so is “unethical”.

Tedros Adhanom Ghebreyesus cautioned against calls in some countries to let Covid-19 run its course until enough people develop the immunity needed to naturally halt its spread.

The concept has been frequently referenced since the beginning of the pandemic, and suggests that lockdowns could be avoided by allowing the virus to spread amongst communities while putting in safeguards to protect those most at risk.

The hope is that, eventually, a natural immunity to the disease is developed.

However, Tedros pointed out that the process has never been used as a strategy for responding to an outbreak, let alone a pandemic.

“Herd immunity is a concept used for vaccination, in which a population can be protected from a certain virus if a threshold of vaccination is reached,” he said during a virtual press briefing.

For measles, for instance, it is estimated that if 95% of the population is vaccinated, the remaining five percent will also be protected from the spread of the virus. For polio, the threshold is estimated at 80%.

“Herd immunity is achieved by protecting people from a virus, not by exposing them to it,” Tedros said.

In the early days of Covid-19, it appeared the UK government was pursuing such a strategy but that quickly changed as lockdown measures were introduced amid a sharp spike in cases, hospitalisations and deaths. 

The National Public Health Emergency Team’s epidemiological modelling advisory group chair Professor Philip Nolan recently said there was no guarantee herd immunity would work and is ethically questionable.

His comments were echoed by Tedros, who said that relying on naturally obtaining herd immunity in such a situation would be “scientifically and ethically problematic”.

“Allowing a dangerous virus that we don’t fully understand to run free is simply unethical. It’s not an option.”

He pointed to the lack of information on the development of immunity to Covid-19, including how strong the immune response is and how long antibodies remain in the body.

Tedros pointed to some cases where people are believed to have been infected with the virus a second time.

He also stressed the many long-term health problems of infection, which researchers are only just beginning to understand.

And he pointed out that it has been estimated that less than 10% of the population in most countries are believed to have contracted the disease.

“The vast majority of people in most countries remain susceptible to this virus,” he said.

“Letting the virus circulate unchecked therefore means allowing unnecessary infections, suffering and death.”

Overall, it is estimated that 0.6 percent of people who contract Covid-19 die from the disease, Maria Van Kerkhove, WHO’s technical lead on the virus, told Monday’s briefing.

“That may not sound like a lot,” she acknowledged, stressing though that it “is a lot higher than (for) influenza”.

She also pointed out that “the infection fatality ratio increases dramatically with age.”

While the elderly and people with underlying health conditions are clearly most likely to fall seriously ill from Covid-19, Tedros stressed that they are not the only ones at risk.

“People of all ages have died,” he said.

© AFP 2020 with reporting from Sean Murray.