Hong Kong bet on zero-Covid. Now it's facing a 'preventable disaster'
https://edition.cnn.com/2022/03/05/asia/hong-kong-covid-crisis-intl-hnk-dst/index.html
Strict separation means Covid patients without heavy symptoms can be isolated in hospitals. It will cause following heavy patients to be rejected by hospitals, because many hospitals are occupied by patients with light or no symptoms.
Otherwise, vaccination rate and vaccine species would be related with surging patients.
Second Vaccination rate is less than 70%, and some are prescribed SinoVac vaccine, which shows less effectiveness. Furthermore, Moderna vaccine is not available. These 3 factors can be contributed to severity rate.
Other possibility is natural antibody. Extremely few cases in Hong Kong mean many Hong Kongers are not exposed to Covid-19. So, they are more unlikely to have antibodies against Covid-19.
