U.K. Approves Covid-19 Booster Shot Aimed at Omicron

“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,”

June Raine,

chief executive of Britain’s Medicines and Healthcare products Regulatory Agency, said Monday.

Variant vaccines are likely to play a role in fall booster campaigns in the hope that they can strengthen immune protection against newer strains of the virus. The Covid-19 vaccines currently available are based on the original strain of SARS-CoV-2. The protection afforded by those shots has been blunted by the rise of successive new variants, although studies have shown that boosting can restore immunity. No variant has so far been found to totally evade immune defenses acquired from earlier vaccination or infection.

Britain’s MHRA said the approval was based on clinical trial data showing that a booster with the bivalent Moderna vaccine triggered a strong immune response against Omicron BA.1 and the original strain. It said exploratory analysis found that the bivalent vaccine also generated a good immune response against Omicron subvariants BA.4 and BA.5 that are driving waves of infection in some parts of the world. The agency has approved the shot for use in adults.

For the U.S. market, Moderna is developing a separate vaccine that targets the BA.4 and BA.5 Omicron variants, after the Food and Drug Administration in late June recommended that vaccine makers pursue new booster shots aimed at those strains. The highly contagious BA.5 strain now accounts for nearly 90% of all infections in the U.S., according to the latest variant-tracking data from the Centers for Disease Control and Prevention.

In the U.K., Moderna said it is working with health authorities to make the bivalent vaccine available in Britain in light of its approval. Earlier supply contracts with the U.K. government included access to modified vaccines to contend with potential variants of concern.

An expert committee that advises the U.K. government on vaccine strategy said Monday that it would recommend the bivalent shot alongside some existing vaccines for a fall booster campaign aimed at adults aged 50 and older, as well as certain other groups such as front-line healthcare workers and people with weakened immune systems.

The committee said in a written statement that all of the available booster vaccines offered good protection against severe Covid-19. In addition to Moderna’s bivalent shot, it recommended the company’s original vaccine as well as the existing vaccine from

Pfizer Inc.

and partner

BioNTech

SE. It also said the vaccine from

Novavax Inc.

could be used in some circumstances.

Stéphane Bancel,

chief executive of Moderna, said the U.K. approval was the first time any vaccine that targeted Omicron alongside the original strain had been authorized. Moderna has also applied to regulatory authorities in Australia, Canada and the European Union and expects further decisions in the coming weeks, the company said.

Studies by Moderna and other manufacturers, including Pfizer and BioNTech, have shown that tweaking their original shots to target new strains of the virus might nudge the antibody response in the direction of new variants. But those studies didn’t determine whether that broader immune response meant the variant shots decreased the risk of developing symptomatic Covid-19 compared with vaccines based on the original strain.

Pfizer and BioNTech have developed an Omicron-targeting update to their Covid-19 vaccine, while

Sanofi SA

and

GSK

PLC have a modified vaccine targeting the Beta variant of the virus.

Moderna began testing the bivalent booster, dubbed mRNA-1273.214, in a continuing trial in March. It said the bivalent shot elicited a greater neutralizing antibody response against Omicron—and boosted antibodies against the original strain to higher levels—when compared with a booster shot of the original vaccine.

Write to Denise Roland at Denise.Roland@wsj.com