A medical worker injects COVID-19 vaccine for a senior citizen in Dongcheng District of Beijing, capital of China, April 18, 2022. Photo:Xinhua

China is likely to roll out a second booster shot, or the fourth shot, for high-risk groups, including those aged 60 and above and those with serious underlying disease or hypoimmunity, the Global Times learned from a source close to China's disease control and prevention system.

The Chinese disease control and prevention system is holding a video training for its staff providing guidance on the issue, according to the source.

A total of nine combinations of inoculation have been approved in China. People from the above-mentioned groups can apply for a fourth shot after at least six months of their third shot, the source said.

People who had accepted three inactivated vaccines can apply for one of eight other vaccines that had been approved for emergency use as a fourth shot. The eight vaccines include the inhaled recombinant vaccine (Adenovirus Type 5 Vector) developed by CanSinoBIO, the nasal spray vaccine developed by Beijing Wantai Biological Pharmacy and a bivalent protein vaccine developed by SinoCellTech, according to the source.

Those who had accepted two CanSinoBIO vaccines are also eligible for the company's inhaled recombinant vaccine as a second booster shot, the source said.

Vaccines based on the mucosal immunological mechanism would be better choices as they proved to be safer and more effective according to studies, the source noted.

Intensive research and development efforts for COVID-19 vaccines in China have provided residents in the country with continually improving vaccines, but, at the same time, it also brings about difficulty in calculating vaccination data according to different combinations, the source said.

The move comes as China continues encouraging high-risk groups, especially seniors and people with underlying diseases, to accept vaccinations amid spreading of highly contagious Omicron variants like BF.7 and BA.5 in some cities.

According to training materials provided by the source, as of Sunday, 85.7 percent of Chinese people aged 60 and above had accepted booster shots, the rate was 91.4 percent among those aged 60-79 and 73.9 percent among those aged 80 and above.

Local authorities in some places have set up vaccination goals among seniors by the end of January, 2023, according to media reports.

In Yexian county, Central China's Henan Province, local authorities had issued documents to promote vaccination among seniors. The document required that, by the end of January, 2023, 90 percent of local seniors aged 80 and above should accept at least one shot, while 90 percent of the target group who are qualified for vaccination should complete full vaccination and accept booster shots.

By the same period, at least 95 percent of those aged 60-79 should complete either be fully vaccinated or have received booster shots, according to the document.

Other regions including Kunming in Southwest China's Yunnan Province, Erdos in North China's Inner Mongolia Autonomous Region, Yushu in Northwest China's Qinghai Province and Xuanhan county in Southwest China's Sichuan Province, introduced similar goals, according to media reports.

Wang Huaqing, chief immunologist at the Chinese Center for Disease Control and Prevention, also called on seniors to get vaccinated as soon as possible.

It does take a certain period of time for the vaccine to exert a protective effect after vaccination, Wang said. Generally, antibodies will begin to be produced within 1-2 weeks following the vaccination; if a relatively high level of antibodies are to be produced, it takes about four weeks after full inoculation, Wang explained at a press conference of the Joint Prevention and Control Mechanism of the State Council on Tuesday.

Booster shots can trigger higher levels of antibodies in a shorter period of time. So, elderly people should get vaccinated as soon as possible to achieve better protection, Wang noted.