At least two Chinese provinces have announced they will administer booster shots against COVID-19 to specific target groups, amid growing calls worldwide for further protection against the coronavirus in the form of an additional dose.

On Friday, health authorities in the eastern province of Zhejiang said they would start giving booster shots to fully vaccinated adults between the ages of 18 and 59 in “key groups.” Those eligible for the extra shot include health care workers and customs officials.

Xia Shichang, the deputy head of Zhejiang health commission, said the move was part of a national plan set to begin late September to offer an additional COVID-19 shot to fully vaccinated individuals. However, China’s central government has yet to announce a plan on providing additional vaccine doses to its population.

Zhejiang’s announcement came just a day after authorities in the central Henan province became the first to announce a booster shot program, though details were scant. Both provinces haven’t disclosed which of the seven COVID-19 vaccines — fully approved or for emergency use in China— would be used for the booster shot.

In recent weeks, several high-income countries — including Israel, Germany, the Czech Republic, and the United States — have either kicked off or announced plans to start booster shot programs, despite the World Health Organization’s call to halt them over growing vaccine inequity.

As of Wednesday, China had fully vaccinated over 1 billion people, more than 70% of the country’s population, according to Lei Zhenglong, a senior official with China’s National Health Commission. While the coverage is among the world’s highest, the highly contagious delta variant has repeatedly broken through the country’s defenses against the virus.

Just weeks after China contained one of its largest outbreaks that started in the eastern city of Nanjing, the country is facing another COVID-19 surge in the coastal Fujian province. The province has reported more than 200 infections since the first cases were identified among two school children last Friday.

While the source of the outbreak remains unclear, experts said a returnee from Singapore may have contracted the virus during his quarantine. The man is said to be the father of one of the infected students.

The Fujian provincial government hasn’t released the vaccination status of the infected patients, though authorities in the city of Quanzhou said 11 of the 18 infected patients discovered there were fully vaccinated. Most of the initial cases found among airport workers in Nanjing were also fully vaccinated, according to a top doctor at a city hospital.

Experts say that breakthrough infections — when a fully vaccinated person becomes infected — are expected, as no coronavirus vaccine is 100% effective in combating the disease. In particular, the Chinese vaccines are about 50% to 78% effective against COVID-19, relatively lower than the efficacy of several Western vaccines.

“The move (to provide booster shots) is likely because the disease season is around the corner,” Yang Zhanqiu, a virologist at Wuhan University, told Sixth Tone, adding that winter is peak time for respiratory pathogens, including the coronavirus, to spread. “But whether a booster shot can actually offer more protection — and if so, how you do it — are scientific questions that need data to answer,” he said.

According to a yet-to-be peer-reviewed paper published in July, Chinese researchers found a notable drop in people’s antibody levels six months after becoming fully vaccinated with the vaccine developed by Beijing-based Sinovac — one of the most widely used COVID-19 vaccines in China. The level of antibodies in the blood is generally linked to the level of protection against pathogens.

The study also showed a third shot six months after the designated two-dose regimen could increase antibody levels by at least threefold.

Nevertheless, the current Chinese-developed vaccines — including one from Sinovac — can significantly reduce the disease’s severity even in case of breakthrough infections, an international panel of scientists concluded in a recently published paper. The panel, therefore, didn’t recommend booster shots for the general population for now, suggesting instead to give vaccine supplies to unvaccinated populations in other parts of the world.

Editor: Bibek Bhandari.

(Header image: A high school student receives COVID-19 vaccine in Zhengzhou, Henan province, Aug. 17, 2021. People Visual)