The risk of being admitted to hospital is up to 70% less for people with Omicron compared to those infected with Delta, according to the first UK government study of its kind.
The UKHSA said the new variant was more transmissible than previous ones such as Delta, and could still lead to significant numbers of people needing hospital treatment over the coming weeks.
At the same time, the preliminary UKHSA data suggests that protection against Covid starts to wane 10 weeks after a booster jab, raising the prospect that a fourth dose of vaccine may be required for some in 2022.
It has already been established that protection against symptomatic disease wanes after a second dose of vaccine, and then improves after a booster. However, the new UKHSA data suggests this extra protection starts to decrease more rapidly against Omicron than Delta, being about 15% to 25% lower from 10 weeks after the booster dose.
The Joint Committee on Vaccination and Immunisation, the body that would decide on whether a fourth dose is required, has begun assessing the UKHSA data. One health official suggested that a first dose of a new vaccine specially targeted at Omicron might be a better option than a fourth dose of the same vaccine.
The new data emerged after the UK experienced yet another record-breaking number of daily reported Covid cases, with 119,789 reported as of 9am on Thursday.
The UKHSA said Omicron now accounted for 76% of Covid cases in England, making it the dominant variant. The areas with the highest rates of Omicron are London (90.2%) and the east of England (80%), while the lowest are the north-east (56.8%) and Yorkshire and Humber (71%).
