Using the principle of so-called "herd immunity" to stem the COVID-19 pandemic is "unethical" and "not an option" countries should pursue to defeat the virus, the UN health agency chief warned on Monday.

世界卫生组织总干事谭德塞警告称，用所谓的“群体免疫”原则来阻止新冠肺炎疫情是“不道德的”，也不是国家抗击病毒的“一个选项”。

"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", Tedros Adhanom Ghebreyesus, Director-General of the World Health Organization (WHO), told the agency's regular press briefing in Geneva.

But, he explained, it is achieved by protecting people from the virus, "not by exposing them to it".

"Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak”, the WHO chief said, calling it "scientifically and ethically problematic".

To obtain herd immunity from measles, for example, about 95 percent of the population must be vaccinated. However, according to WHO estimates, less than 10 percent of the global population has any immunity to the coronavirus, leaving the "vast majority" of the world susceptible.

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