Sinovac boosters provide key protection for older people, new study finds

Two doses of China’s Sinovac vaccine offered older people only a moderately high level of protection against severe disease and death from COVID-19, but a third dose significantly bolstered their defenses, according to a new study by scientists in Hong Kong.

The study, based on patients infected during the current devastating omicron wave in Hong Kong, serves as a cautionary note for mainland China, where Sinovac is a pillar of the country’s vaccination program. Many older people there have yet to receive booster shots.

For people 60 and older, two Sinovac doses were 72 percent effective against severe or fatal COVID-19 and 77 percent effective against COVID-related death, the study found. Those levels of protection were lower than those provided by two Pfizer-BioNTech doses. The same study found they were 90 percent effective against severe or fatal COVID and 92 percent effective against death among Hong Kong residents of the same age group.

A Sinovac booster shot helped considerably, proving to be 98% effective against severe or fatal COVID among people at least 60 years old, the study found.

Yanzhong Huang, a global health expert at the Council on Foreign Relations, said that the results highlighted the urgency for mainland China to accelerate its lagging booster campaign. “There’s a lot of work for the government to do to make sure this segment of the population receives the booster shots,” he said.

The study’s authors, who are scientists at the University of Hong Kong, noted that the city’s booster program began just recently, making it difficult to determine how long protection from a third dose would last.

Sinovac, a private Chinese company that makes the vaccine, is one of two manufacturers of COVID shots available in China. Vaccines using mRNA technology, like those made by Pfizer-BioNTech and Moderna, are not available there.

The new study highlights the potential consequences for China, which has relied heavily on Sinovac and is battling its biggest COVID outbreak in two years. More than 87% of China’s population has been vaccinated. But just over half of people 80 and older have had two shots, and less than 20% of people in that age group have received a booster, Zeng Yixin, a vice minister of the National Health Commission, said recently.

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