Population groups with a high risk of infections, especially people aged 60 and above, people with serious underlying health conditions and those with low immunity are advised to receive a second booster shot six months after the first, the report said. Those who have received three doses of inactivated vaccines can choose a different type of vaccine -- recommended by the government -- for the second booster, namely a recombinant protein vaccine, an adenovirus vector vaccine or an influenza virus vector vaccine, according to experts.
