Sinovac Booster offers seniors stronger protection against the Micron, according to a study

Two doses of the Chinese Sinovac vaccine offered seniors only a moderately high level of protection against serious illness and death from Covid-19, but a third dose significantly strengthened their defenses, according to a new study by Hong Kong scientists.

The study, based on patients infected during the current devastating Omicron wave in Hong Kong, serves as a warning for mainland China, where Sinovac is a mainstay of the country’s vaccination program. Many older people have not yet received booster shots.

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

A booster injection of Sinovac helped greatly, proving 98% effective against severe or fatal Covid among people aged 60 or over, the study found.

Yanzhong Huang, a global health expert at the Council on Foreign Relations, said the findings highlighted the urgency for mainland China to accelerate its overdue recall campaign. “There is a lot of work for the government to do to make sure this segment of the population gets the recall,” she said.

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

As people with underlying health conditions in Hong Kong were more likely to resist vaccination, they said, it was also possible that those who chose to be vaccinated or boosted were healthier in the first place, inflating estimates than they initially were. protective vaccines.

Sinovac, a privately held Chinese company that makes the vaccine, is one of two Covid vaccine manufacturers available in China. Vaccines that use mRNA technology, such as 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 largest Covid epidemic in two years. More than 87% of the Chinese population has been vaccinated. But just over half of people aged 80 and over have had two vaccinations, and fewer than 20 percent of people in that age group have received a booster, Zeng Yixin, deputy minister of the National Health Commission recently said.

The new Hong Kong study received funding from the Chinese Center for Disease Control and Prevention as part of what one study co-author described this week as an effort to understand the comparative efficacy of vaccines. It was published online as a prepress, but has not yet been vetted by peer scientists for publication in a scientific journal.

The study found that Sinovac’s vaccine worked similarly to Pfizer’s among young people, even without a booster dose. In people younger than 60, two doses of Sinovac were about 92% effective against severe or fatal Covid, while two doses of Pfizer were about 95% effective.

Neither vaccine provided much protection against mild or moderate Covid, although Pfizer offered more than Sinovac and a booster dose greatly increased levels of protection. During the last wave, people in Hong Kong were largely infected with the Omicron sub-variant known as BA.2. Like other versions of Omicron, BA.2 has infected many vaccinated people.

The Hong Kong wave is killing people at a rate faster than most countries since the coronavirus emerged, a result, in large part, of low vaccination rates among older residents. Nearly 90 percent of people who died during the last wave were not fully immunized, suggesting that giving vaccinations to the most vulnerable is more important than the particular brand of vaccine.

Like Hong Kong, mainland China had largely succeeded in suppressing transmission of the virus before Omicron, leaving its population with very little immunity from previous infections.

In addition to China, Sinovac vaccines have also been instrumental in protecting people from severe Covid, especially in poorer countries. The vaccine is used in 49 countries, including South America and Africa.

But concerns about the protection it offered had already prompted the World Health Organization to recommend in October that recipients 60 years of age and older should receive a third dose.

Dr Andrew Morris, an infectious disease specialist at Sinai Health and University Health Network in Toronto who was not involved in the Hong Kong study, said the findings fit laboratory studies suggesting that Sinovac generated higher levels. low in neutralizing antibodies compared to vaccine mRNAs, such as Pfizer’s.

“I think what we’re going to see is that in countries that have relied heavily on Sinovac, if they don’t have boosters, especially with an mRNA booster, or even with Sinovac, they’re likely to struggle with high rates of infection from this latest BA wave. 2, “he said.

Dr Morris said the results in Hong Kong, like those of other vaccine studies, also strongly depended on how long it had been since people had been given the injections. The protection tends to weaken over time.

The results of the latest study on the efficacy of the third dose of Sinovac could be taken as an encouraging signal by Chinese leaders that Chinese-made vaccines could remain at the heart of their immunization campaign, said Dr. Huang, of the Council on Foreign Relations.

“Now, for Chinese leaders, they don’t need to face heavy pressure to approve BioNTech’s vaccine,” he said.