Getting a COVID-19 vaccination is one of the most effective ways of reducing the risk of severe illness and death among the elderly and people with preexisting medical conditions, a health expert said on Wednesday.

Wang Huaqing, chief immunization expert at the Chinese Center for Disease Control and Prevention, said that at one designated hospital in Jilin province, only 15 percent of severe and critical patients had received two shots, far behind the national average vaccination rate.

The Omicron variant is highly transmissible and invasive and has increased the risk of infection, Wang said.

Given that it has become the dominant variant in recent outbreaks, people who have not yet been vaccinated should do so immediately as the treatment usually takes effect after 14 days, he said.

Lei Zhenglong, deputy head of the Bureau of Disease Prevention and Control at the National Health Commission, said that as of Tuesday, the country has administered more than 3.28 billion doses of COVID-19 vaccines, covering almost 1.28 billion people, and that more than 1.24 billion have been fully vaccinated.

Almost 90 percent of the country has been fully vaccinated against the novel coronavirus and nearly 757 million people have received COVID-19 booster shots, he added.

More than 224 million seniors aged 60 or above have been vaccinated, 213 million of them have been fully vaccinated and almost 147 million have received booster shots, Lei said.

The situation remains complicated and grim and vaccination is an effective way to strengthen protection against the virus, he said.

The commission and local authorities have made arrangements to make vaccinations more convenient for the elderly, and people should get vaccinated, he added.