Washington, Dec 27 (IANS): Amid the rapid spread of the Omicron variant in the US, New York City has seen a four-fold rise in children being hospitalised for Covid-19 since early December.

According to the New York State Health Department, the increase was observed in children 18 and under beginning the week of December 5 through the current week, ABC News reported.

At the time of hospitalisation, none of the 5- to 11-year-olds with Covid-19 were fully vaccinated, the Department said.

However, about one-third of 12- to 17-year-olds admitted due to Covid-19 are fully vaccinated.

"The risks of Covid-19 for children are real," acting State Health Commissioner Mary Bassett said in a statement.

"We are alerting New Yorkers to this recent striking increase in paediatric Covid-19 admissions so that paediatricians, parents and guardians can take urgent action to protect our youngest New Yorkers."

About 27 per cent of 5- to 11-year-olds and nearly 72 per cent of 12- to 17-year-olds in New York state have received at least one vaccine dose, state data shows.

"Unfortunately NY is seeing an increase in paediatric hospitalisations (primarily amongst the unvaccinated), and they have similar (5- to 11-year-old) vaccination rates," Erica Pan, the California state epidemiologist, said on Twitter.

"Please give your children the gift of vaccine protection as soon as possible as our case (numbers) are increasing rapidly," she added.

The State Department of Health issued an advisory reminding parents to "not assume a mild respiratory illness" as a routine "cold", but to test for Covid-19.

"Although Covid-19 is usually mild in children, there are risks of serious illness and sequelae for children, and if not isolated they can contribute to community transmission," the statement read.

The advisory also "strongly" recommended Covid-19 vaccination for children age 5 and up and boosters for those eligible; wearing a wellfitting mask, social distancing, and avoidance of crowds.