The highly contagious Omicron variant accounted for 99.9 per cent of new weekly Covid-19 infections in the US, according to data updated by the US Centers of Disease Control and Prevention (CDC).

The Delta variant, which spiked last summer, only made up the remaining 0.1 per cent in the week ending January 29, Xinhua news agency reported.

The new infections driven by Omicron have risen rapidly since early December. The variant accounted for only 0.6 per cent of new cases in the week ending December 4, rising to 89.3 per cent in the week ending January 1, and 97.8 per cent in the week ending January 15, CDC data showed.

Several studies have suggested current authorised Covid-19 vaccines could provide strong protection against hospitalization and death caused by the Omicron variant.

During both Delta and Omicron predominance, incidence and hospitalization rates were the highest among unvaccinated persons and the lowest among vaccinated persons with a booster, according to a report published by the CDC on Tuesday.