New data suggesting Omicron may be less likely to lead to serious illness than the Delta variant of coronavirus offers a “glimmer of Christmas hope”, a senior health official has said.

But UK Health Security Agency (UKHSA) chief executive Dr Jenny Harries warned that it is too early to downgrade the threat from the new strain, which is still spreading rapidly across the UK.

Dr Harries told BBC Radio 4’s Today programme that more information is needed, particularly about the impact on elderly and more vulnerable patients.

She added: “There is a glimmer of Christmas hope in the findings that we published yesterday, but it definitely isn’t yet at the point where we could downgrade that serious threat.”

The UKHSA estimates that someone with Omicron is between 31% and 45% less likely to attend A&E and 50% to 70% less likely to be admitted to hospital than an individual with the Delta variant.

The rapid spread of Omicron has seen it become the “dominant strain now right across the UK”, and Dr Harries said cases are still doubling across “most regions” of the country.

She added: “What we have got now is a really fine balance between something that looks like a lower risk of hospitalisation – which is great news – but equally a highly transmissible variant and one that we know evades some of our immune defences, so it is a very balanced position.”

The UKHSA data has fuelled speculation in Westminster that further restrictions can be avoided in England after Christmas.

In Scotland, nightclubs will close for at least three weeks from December 27 as part of a package of measures to control the spread of the virus, while clubs in Wales and Northern Ireland will close from Boxing Day.

Health Secretary Sajid Javid has warned that Omicron still has the potential to overwhelm the NHS despite the “promising” data because it is more infectious than past variants.

In Scotland, First Minister Nicola Sturgeon used her Christmas message to urge people to get vaccinated, describing the booster campaign as “a source of brightness during a really difficult month”.

Extra military personnel are also being drafted in to help ambulance services across the country struggling with a high number of staff absences due to Covid.