https://www.cnbc.com/2022/02/07/chinas-zero-covid-policy-will-not-work-with-omicron-epidemiologist.html
China is "uniquely at risk" to omicron, Osterholm said, for a combination of reasons: Early studies suggest its Sinovac and Sinopharm vaccines are "not very effective" against the variant, and at the same time China's success at preventing the spread of Covid so far means it has a very large population that remains vulnerable.
Herd immunity is full proof. That's why stuff like smallpox and syphilis are only from the ancient past and wasn't a problem through most of recorded history up until vaccines.