The UK medicines regulator (MHRA) approved the so-called bivalent vaccine made by U.S. drug company Moderna as a booster for adults.
The agency's decision was based on clinical trial data that showed the booster triggered "a strong immune response" against both omicron (BA.1) and the original 2020 virus, it said.
The MHRA also cited an exploratory analysis in which the shot was found to generate a good immune response against the currently dominant omicron offshoots BA.4 and BA.5.
No serious safety concerns were identified with this new formulation, the agency added.
Now approval has been secured, Britain's Joint Committee on Vaccination and Immunization (JCVI) will advise on how the vaccine should be deployed in the country.
While existing COVID-19 vaccines continue to provide good protection against hospitalization and death, vaccine effectiveness has taken a hit as the virus has evolved.
"The first generation of COVID-19 vaccines being used in the UK continue to provide important protection against the disease and save lives," MHRA Chief Executive June Raine said in a statement.
"What this bivalent vaccine gives us is a sharpened tool in our armory to help protect us against this disease as the virus continues to evolve."
European Medicines Agency (EMA) officials expect COVID variant-adapted vaccines to be approved in the European Union by September, and have signaled 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.
In contrast, the U.S. 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.
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 yea. (NS/VOA)