Each dose of the booster shot will target both the original COVID virus that was first detected in 2020 and the omicron BA.1 variant.
British drug regulators have become the first in the world to authorise an updated version of Moderna's coronavirus vaccine that aims to protect against the original virus and the omicron variant.
In a statement on Monday, the UK's Medicines and Healthcare Regulatory Agency (MHRA) said it had given the green light to Moderna's combination "bivalent" vaccine, which will be used as an adult booster shot.
Each dose of the booster shot will target both the original COVID-19 virus that was first detected in 2020 and the omicron BA.1 variant that was first picked up in November.
British regulators said the side effects were similar to those seen for Moderna's original booster shot and were typically "mild and self-resolving".
"What this (combination) vaccine gives us is a sharpened tool in our armoury to help protect us against this disease as the virus continues to evolve," said Dr June Raine, the head of Britain's health care and medicines regulator.
Such an approach is used with flu shots, which are adjusted each year depending on the variants that are circulating and can protect against four influenza strains.
Stephane Bancel, Moderna's Chief Executive, said in a statement that it was the first regulatory authorisation for a vaccine aiming to fight the omicron variant, predicting the booster would have an “important role” to play in protecting people against COVID-19 in the winter.
Britain's health officials have not yet decided whether or not the tweaked vaccine will be used in its fall strategy. In July, the government said everyone 50 and over would get a COVID booster in the fall.
EU approval of COVID variant vaccines
The European Medicines Agency (EMA) officials expect COVID variant-adapted vaccines to be approved in the European Union by September and have signalled the regulator is open to using shots targeting the older BA.1 variant this autumn, given those specifically targeting newer subvariants are further behind in clinical development.
On Friday, Germany's health minister said the European Medicines Agency might clear the tweaked COVID-19 booster next month.
In contrast, the US Food and Drug Administration (FDA) has said it will seek the specific inclusion of the newer BA.4 and BA.5 offshoots of Omicron in any new shots used domestically.
According to the World Health Organization (WHO), the latest global surge of COVID-19 has been driven by omicron subvariant BA.5, which is responsible about 70 per cent of the virus samples shared with the world's largest public virus database.
Apart from Moderna, partners Pfizer Inc and BioNTech have also been testing versions of their mRNA vaccine modified to combat Omicron variants.
Meanwhile, Sanofi and partner GSK are working on a protein-based vaccine that targets the Beta subvariant, which dominated for some time last year.