Among those admitted during the omicron surge, vaccinated adults had less severe illness compared with unvaccinated adults and were less likely to land in intensive care, finds a new study.

The study, by Cedars-Sinai Medical Center and the Centers for Disease Control and Prevention (CDC), showed that during the Omicron period fewer patients died while hospitalised (4 per cent), compared with those admitted when the delta variant was dominant (8.3 per cent).

"Overall, the Omicron-period group had a lower likelihood of being admitted to the intensive care unit (ICU) and were also less likely to require invasive mechanical ventilation compared with the Delta-period group," said researcher Matthew Modes from Cedars-Sinai Medical Center in the US.

In a single-hospital study, published in the CDC's Morbidity and Mortality Weekly Report, the team looked at the characteristics of 339 patients hospitalised with COVID-19 at Cedars-Sinai in Los Angeles, from July to September of 2021, when the Delta variant of SARS-CoV-2 was dominant. They compared that group with 737 patients admitted with COVID-19 during December 2021-January 2022, when the Omicron variant was most prevalent.

The analysis revealed that a greater portion of the patients hospitalised during omicron was vaccinated as compared to patients hospitalised during the summer of 2021 when the delta variant predominated, likely reflecting the higher percentage of the populations that were vaccinated during omicron.