London: 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).

'Bivalent' vaccines

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.

US biotech company Moderna said in June that the so-called "bivalent" vaccine, which targets the original Covid strain and original Omicron BA.1, performed better against both compared to its original Covid vaccine called Spikevax.

The EU's medicines watchdog said that month it had started to review the new vaccine.

The European agency is also studying a rival adapted jab developed by Pfizer/BioNTech, which it has said it aims to approve this autumn.

The Pfizer/BioNTech jab is adapted for the BA.4 and BA.5 types of the virus.

The BA.4 and BA.5 variants were first discovered in South Africa and spread rapidly despite high population immunity conferred by prior waves and vaccinations.

Like other Omicron variants, they tend to have a milder disease course as they settle less in the lungs and more in the upper nasal passages, causing symptoms like fever, tiredness and loss of smell.