Altogether 16 out of the current 18,170 COVID-19 patients in hospitals in Shanghai  are in severe condition, the Shanghai government said on Sunday.

The city, which is experiencing its worst COVID-19 outbreak in two years, has reported more than 340,000 local infections since early March with the majority  of cases being asymtomatic.

All the severe cases, including 15 aged 70 or above, are receiving personalized medical treatment from multidisciplinary teams at designated hospitals, said Wu Jinglei, director of the Shanghai Municipal Health Commission.

"All the severe cases suffer from serious underlying diseases," said Wu.

One case, 33, is a patient of severe autoimmune disease. All the elderly severe cases suffer from diabetes, cardiovascular and cerebrovascular diseases, malignant tumors, pulmonary embolism, and chronic obstructive pulmonary disease.

"While actively treating the novel coronavirus pneumonia, these patients are treated with ventilator-assisted ventilation, extracorporeal membrane lung (ECMO), anti-virus and anti-infection therapies, and symptomatic nutritional support," Wu said.

Only one of them received two shots of the COVID-19 vaccine, according to the health commission.

The commission reminded elderly residents without contraindications to complete the full vaccination regimen and receive booster shots as soon as possible, as vaccines play an important role in helping prevent the elderly population from developing into severe cases in case of contracting the virus.

Shanghai registered 3,238 locally transmitted COVID-19 confirmed cases and 21,582 asymptomatic infections on Saturday.