by BLOOMBERG / pic by AFP

THE omicron variant of Covid-19 has been linked to more hospitalisations, severe complications and deaths of young children than previous waves of the virus, suggesting the highly contagious strain may not be as mild as initially thought, according to a Hong Kong-based study.

Researchers from the University of Hong Kong and Princess Margaret Hospital reviewed child hospitalisations during different stages of the pandemic. They found that cases were far more severe in the omicron wave that continues to sweep through the city in its worst outbreak of the pandemic.

A total of 1,147 children aged 0-11 were hospitalised in Hong Kong due to Covid-19 from Feb. 5 to 28, more than 80% of whom were 0-5 years old.

The need for intensive care treatment for those hospitalised was higher for omicron, with 21 children – or 1.83% – admitted to pediatric ICU, compared with only one in all the previous Covid outbreaks in Hong Kong, and a 0.79% rate for those with influenza.

For the 22 months from the start of 2020 to November 2021, a period covering four previous waves that didn’t penetrate Hong Kong nearly as widely as the current outbreak, 737 children aged 0-11 were hospitalised due to Covid.

Omicron results in a higher number of seizures among unvaccinated children and targets the upper airways more than previous variants and influenza, the researchers said in a preprint paper submitted to The Lancet on March 21.

“The intrinsic severity of omicron BA.2 is not mild as evident by the fatality and severe complications of the uninfected and unvaccinated children,” they wrote in the paper, which hasn’t been peer reviewed.

Globally, the elderly and people with pre-existing medical conditions have been most vulnerable to the virus throughout the pandemic. After a long run of keeping infection rates among the lowest in the world, Hong Kong was overrun with omicron, which has been linked to almost 7,500 deaths. The majority of those were elderly and unvaccinated.

One reason why some infected children under 5 in Hong Kong are experiencing severe symptoms could be due to a lack of exposure to the coronavirus over the past two years, so they haven’t built up immunity, the researchers said. Children under 11 were only approved for Covid vaccinations in February, while those under 3 still aren’t eligible.

“Vaccination should be rapidly implemented for children eligible, and in particular for under 3 years old, extension of use of current vaccines should be urgently explored,” the researchers wrote. 

Among the 1,147 omicron hospitalisation cases, four children died, including three who had good past health. They were aged 11 months, 3 and 4. None of the three were vaccinated against the virus. Of the cases from January 2020 to November 2021, there were no deaths associated with the virus.

The fatality rate of omicron in the February stage of the study was 0.35% for hospitalised children, higher than influenza at 0.05%. The figure, however, is likely an overestimate because many children with mild omicron symptoms weren’t taken to the hospital and instead cared for at home, the researchers said.