The UK's drug regulator said Monday it had approved an updated Moderna vaccine against the coronavirus that targets the Omicron variant as well as the original form.

The Medicine and Healthcare products Regulatory Agency (MHRA) said in a statement said it had approved the vaccine for adult booster doses "after it was found to meet the UK regulator's standards of safety, quality and effectiveness".

It was the first such "bivalent" Covid-19 vaccine to be approved by the British regulator.

The MHRA's chief executive June Raine said data from a clinical trial had shown it prompted a "strong immune response" against the original virus and Omicron, and would provide a "sharpened tool in our armoury" as the virus kept evolving.

While vaccines have helped lower hospitalisations and deaths from Covid, which first emerged in China in late 2019, the current jabs are mainly aimed at the earlier strains of the disease.

The World Health Organization warned in July that the pandemic was "nowhere near over", due to the spread of Omicron subvariants and to the lifting of control measures.

Half of the Moderna vaccine, called Spikevax bivalent Original/Omicron, targets the original 2020 virus and half the Omicron variant (BA.1).

The MHRA said the vaccine was also found to generate a "good response" against two Omicron subvariants, BA.4 and BA.5, which have partly driven a wave of new cases of the disease in Europe and the United States.

It also said the vaccine had the same "typically mild" side effects as the original Moderna jab.