Britain's medicine regulator has approved a coronavirus vaccine made by Moderna that targets both the original strain and the Omicron variant.

The regulator announced on Monday that it gave the green light to the so-called bivalent vaccine from the US drug maker as a booster for adults aged 18 and older.

Officials said a clinical trial showed that the bivalent booster shot triggers a strong immune response against both the BA.1 Omicron subvariant and the original strain.

The bivalent vaccine was also found to generate a good immune response against BA.4 and BA.5 -- two subvariants that are dominant among Omicron infections.

Local media reported that the UK became the first country to approve the Omicron-tailored vaccine.

The chief executive of the Medicines and Healthcare products Regulatory Agency said the vaccine gives Britons "a sharpened tool in our armory to help protect us against this disease as the virus continues to evolve."

Moderna said in a statement that the bivalent vaccine "has an important role to play in protecting people in the UK from COVID-19 as we enter the winter months."

The company said it has completed regulatory submissions for the bivalent shot in Australia, Canada and the European Union. It also applied to Japan's health ministry last week to gain approval for the vaccine.