Omicron variant of coronavirus more infectious than Delta, no milder: Study

The reinfection rate of the Omicron variant of coronavirus is more than five times higher than the Delta variant, a new study has claimed. According to a study by Imperial College London, Omicron was associated with a 5.4-fold higher risk of reinfection compared with Delta.

The protection afforded by past infection against reinfection with Omicron may be as low as 19%, it added.

The study by Imperial College London was based on UK Health Security Agency and National Health Service data and has not yet been peer-reviewed.

Further, the study found an increased risk of developing a symptomatic Omicron case compared to Delta for those who were two or more weeks past their second vaccine dose, and two or more weeks past their booster dose.

Depending on the estimates used for vaccine effectiveness against symptomatic infection from the Delta variant, this translates into vaccine effectiveness of between 0% and 20% after two doses, and between 55% and 80% after a booster dose, the study added.

"This study provides further evidence of the very substantial extent to which Omicron can evade prior immunity given by both infection or vaccination," study lead Professor Neil Ferguson said in ICL's statement.

“This level of immune evasion means that Omicron poses a major, imminent threat to public health,” he said.

The data analysed by Imperial College was based on 333,000 cases, including 122,062 of Delta and 1,846 which were confirmed as the Omicron coronavirus variant through genome sequencing.

Imperial College's Professor Azra Ghani, who co-led the study, described it as "essential for modelling the likely future trajectory of the Omicron wave and the potential impact of vaccination and other public health interventions."

The new findings could accelerate the imposition of tighter restrictions across a number of European countries in a bid to stem the new variant's spread.