'Covid immunity could be higher than official data'
Epidemiologist Benjamin Cowling from the University of Hong Kong (HKU) said on Tuesday that he believes the overall level of immunity against Covid-19 in Hong Kong is significantly higher than official figures suggest.  He was commenting on a new study which found strong antibody responses among recovered Covid patients who then receive a vaccine. Researchers from the HKU and the Chinese University had confirmed that Covid vaccines were more effective when administered to people who have recovered from the coronavirus, compared to those who have never been infected.  Cowling told RTHK's Covid Update programme this is good news. "We consider that infections act as natural boosters and they can replace the dose. What we have in Hong Kong in the population as a whole in the past three months... two-thirds of the population had a natural booster,” he said. “Many of them haven't been documented because we only have about 1.2 million confirmed cases. We think there have been more than four million infections because not every infection is confirmed," he explained. "That means that the level of immunity we have in our population right now than is higher than just reflected by vaccine coverage and the confirmed case numbers."  One of the lead researchers in the study, Professor David Hui from the Chinese University, also noted that people who received a BioNTech jab after an infection were found to have “a very high level” of antibodies – about 144 units, compared to 95 units among people who were triple-jabbed with the vaccine but had not been infected.  He said recovered patients should therefore also consider getting jabbed.  "After their infection, people's antibody level drops gradually. It will drop to a very low level after six months and they may be infected again. They should receive the vaccine three months after their infection to boost their immunity level," he said.