A passenger receives a vaccine at the COVID-19 vaccination bus while he waits for his train at Hangzhoudong Railway Station in Hangzhou, Zhejiang. [Photo/zjol.com.cn]

East China's Zhejiang province has been promoting COVID-19 booster shots since late February in response to China's new vaccination strategy aiming to reinforce herd immunity against the disease.

Known as sequential immunization, the new vaccination method uses different types of vaccines for original and booster inoculations to combine their respective advantages and protect at-risk individuals from side effects brought about by one particular kind of vaccine.

Sequential immunization is often rolled out when dealing with tricky and fast-mutating viruses.

China started the strategy several days ago. People over 18 years old who are fully vaccinated with one of the three inactivated vaccines produced by Sinopharm and Sinovac Biotech are eligible for a sequential COVID-19 booster shot, according to the National Health Commission.

Explaining the new vaccination method and the dos and don'ts after a sequential dose is a major task of medical staff working at vaccination sites in Zhejiang.

Zhang Siqing, a medical worker at a site in Longyou county of Quzhou, said that before delivering booster shots, they would ask for detailed information about people's previous vaccination experiences.

Ye Jiahao, a worker at the disease control and prevention center in Longyou, said they had been given detailed training on sequential immunization in advance of the roll-out.

At a site in Taizhou's Huangyan district, more than 100 sequential booster shots were administered on March 1, according to Zhu Jinli, vice director of the site.