Health authorities are appealing to parents to get their young children vaccinated against Covid-19, as a five-year-old patient remains in critical condition in Tuen Mun Hospital.

Government advisor, Lau Yu-lung, told RTHK on Monday that last month, five children with Covid-19 required intensive care, while a 22-month-old patient died within a short time after getting infected.

Professor Lau said around 2.6 percent of children aged between six months and three years have had the Covid jab since it was made available to that age group from August 4, which he called "a tiny number".

He urged parents not to wait for a BioNTech version, saying the Sinovac jab was just as good at reducing deaths and serious illness.

"I think the initial phase is very hard to convince people. But every one of us keep prodding on and keep explaining and keep presenting the facts to the public, then that number will creep up. When it starts to reach about 20, 30 percent, then you will probably see a fairly rapid rise above 50 or 60 percent", said Lau.

Lau told Janice Wong on RTHK's Hong Kong Today programme that under fives comprised a sizeable proportion of Covid patients currently in hospital.

He warned that if the Omicron subvariants, BA.4 and BA.5, became the predominant strain in Hong Kong, overseas experience showed that hospital admissions would rise.