The World Health Organization has debunked the idea of herd immunity, saying it is "scientifically and ethically problematic" and is not an option. There are some who say the coronavirus be allowed to spread naturally in the lack of a vaccine to achieve immunity in a community.

Herd immunity is achieved by protecting people from a virus not by exposing them to it, said WHO Director General Tedros Ghbreseysus."Allowing a dangerous virus that we don't fully understand to run free is unethical. It is not a option," Tedros said in a statement on Monday. Medical journal Lancet also warned that exposure to the virus does not guarantee future immunity.

The second infection may come with more severe symptoms. The Covid-19 virus has claimed one million lives and still spreading across the world. And there is no vaccine available right now. Tedros made the comments in the context of China which is preparing to test an entire population of the eastern city Qingdao this week.