China will offer a second COVID-19 booster dose to certain groups who had received their first booster shot more than six months ago, authorities said Wednesday.

The targeted groups are people with a high risk of infection, elderly aged over 60 years old, people with serious underlying health conditions, and those with low immunity, according to a circular released by the State Council joint prevention and control mechanism against COVID-19.

All vaccines approved for conditional marketing or emergency use can be used as a second booster dose, according to the document.

It adds that sequential booster immunization, a vaccination strategy that uses different types of vaccines for booster inoculations, or omicron-resistant vaccines, are preferred in choosing second booster doses.

The circular also calls for efforts from health authorities at all levels to ensure vaccination safety and to orderly propel the second booster inoculation program with thorough emergency response plans at vaccination sites and timely updated inoculation information.