A student waits to receive a dose of COVID-19 vaccine at a vaccination point of Wenshu middle school in Nanjing, east China's Jiangsu Province, Aug. 23, 2021. Nanjing started administering the first dose of COVID-19 vaccines among minors aged between 12 and 17. Photo: Xinhua

The city of Shanwei in South China's Guangdong Province took the lead in giving COVID-19 booster shots to key groups of people aged between 18 and 59 who have been fully inoculated with inactivated vaccines for six months, and more cities are about to follow later this month. 

A staff member from the disease control and prevention center in Shanwei confirmed with the Global Times on Thursday that the city has already started to give booster shots to key groups, and some companies have organized their employees to get a third shot. The staff member declined to reveal more information, but he noted that mixed vaccinations are not recommended.

The key groups refer to workers of cold-chain products at ports, loaders, customs officers and public transportation staffers, medical staff and students ready to pursue study abroad, public security officers, community workers and firefighters, and other front-line workers.

Apart from Shanwei, cities in other provinces and regions including North China's Henan and East China's Zhejiang recently also announced plans to give key groups a booster shot if they completed their inoculation for six months. 

Key groups who received two doses of inactivated vaccine before March 1, April 1 and May 1, respectively will get booster shots in September, October and November, according to local disease prevention and control centers in Henan and Zhejiang.

Xia Shichang, deputy head of Zhejiang provincial health commission, said at a press conference on September 17 that the province will give a third shot to roughly about 4 million people working at key posts in batches. 

The Global Times confirmed with some local disease prevention and control centers in Zhejiang on Thursday that they would not start providing booster shots until getting official announcements from authorities. 

"Many people have come to ask about boosters recently, especially those who plan to go abroad. The demand is high as far as I can tell," a staff member from the disease prevention and control center of Hangzhou's Xiaoshan district told the Global Times. 

A senior vaccine expert from the Chinese Center for Disease Control and Prevention confirmed to the Global Times on condition of anonymity that some places have rolled out booster shots plans, but mass vaccination has yet to be decided.

As for when will China greenlight booster shots for the general public, the expert revealed that China will study the safety of this process, and a large amount of data will be acquired before vaccine experts can evaluate whether it's necessary.

The decision will be adjusted and made in accordance with the needs of the domestic COVID-19 resurgence situation, the expert said.

The staffer in Xiaoshan district said Hangzhou will soon give booster shots to key groups after finishing the second shots for children aged 12-14, and the local disease prevention and control center will then release notices to better mobilize key groups to get vaccinated.

China had administered more than 2.1 billion doses as of Wednesday, covering at least 1 billion people.  

Studies have proved that a third shot of a COVID-19 vaccine could boost waning protection over time, and prioritizing people at high risk is essential for China to reduce the risk of the virus spreading from overseas, health experts said. 

At least 10 rounds of flare-ups in China this year could be traced to imported sources, including the recent one in Putian, East China's Fujian Province. 

Another Beijing-based immunologist said the current vaccines perform well in protecting people from severe illness, which means giving boosters to fully vaccinated people is generally not necessary. It wastes resources and increases their risks of having side effects. 

But he suggested giving booster shots to people at a particular time such as in winter, when COVID-19 risks are higher. The high levels of antibodies generated by a third shot will protect them better.

The two giants developing COVID-19 vaccines in China - Sinovac and Sinopharm - have done research on boosters and found antibodies decrease within six months after finishing the entire vaccination process. 

Studies in the United Arab Emirates showed that a third shot of Sinopharm's inactivated vaccine six months after the second one would boost the level of antibodies in recipients by five to 10 times, which would also help to protect recipients from mutations like Delta, the Global Times learned in August. 

A third shot of Sinovac's COVID-19 vaccine given at an interval of six to eight months after the second dose led to a strong boost in immune response, with geometric mean titers (GMTs) increasing to approximately 140, according to a report released in July.