The World Health Organization chief Tedros Adhanom Ghebreyesus on Monday called the herd immunity idea is ''unethical''.

During a press briefing, Tedros said, “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.”

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

“Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic,” he added.

Relying on naturally obtaining herd immunity in such a situation would be "scientifically and ethically problematic", Tedros said.

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

The herd immunity approach was touted by US President Donald Trump as a possible cure of the novel coronavirus.