Chinese drug company Sinovac Biotech said no abnormality related to its coronavirus vaccine has been monitored among people aged above 60, according to feedback from mass vaccinations in China and abroad.

Liu Peicheng, spokesman for Sinovac, said at a press briefing last Sunday that since December, the CoronaVac vaccine developed by the company has been approved for use in nearly 30 countries including China, Brazil, Turkey and Chile.

Liu said in some countries, senior citizens aged above 60 have been given priority for the vaccine, adding that the incidence of adverse reactions after getting the vaccine among people older than 60 is similar to that in adults, according to phase-1 and phase-2 trials in China and mass vaccination results in other countries.

Health officials have been concerned about whether experimental vaccines can safely protect the elderly, whose immune systems usually react less robustly to vaccines.

China's COVID-19 inoculation plan only included people aged between 18 and 59 initially. But some areas in the country have started to vaccinate citizens older than 60 in good health, according to He Qinghua, a senior official from the National Health Commission (NHC).

He said the country will start large-scale vaccine rollout among the elderly after sufficient clinical trial data proved the efficacy and safety of the vaccines. That means China's 254 million senior citizens aged above 60 will be included into the nationwide COVID-19 vaccination campaign.

China has administered over 82.84 million COVID-19 vaccine doses as of Wednesday, according to the NHC.