Britain's Covid booster campaign is set to kick off this September, after the country became the first in the world to approve an Omicron-adapted shot.
Around 26 million people in Britain are estimated to be eligible for an autumn Covid-19 booster, having had at least two Covid vaccine doses already, a UK Health Security Agency (UKHSA) spokesperson said.
The preference is to deploy what is known as a "bivalent vaccine" that targets both the original virus and the Omicron variant through the autumn campaign, but that will depend on the health regulator (MHRA) approving such shots and the state of vaccine supplies.
The UK's Joint Committee on Vaccination and Immunisation (JCVI) has advised boosters should be given to over-50s, individuals in clinical risk groups, frontline workers and care-home staff ahead of the winter, when respiratory viruses are typically at their peak.
On Monday (August 15), the MHRA gave Moderna's bivalent shot conditional approval.
The endorsement of the vaccine is based on data that showed it produced a marginally better immune response against some Omicron variants, versus the original novel coronavirus - although whether that translates into stronger protection against serious disease is unclear.
Contracts with Moderna and Pfizer-BioNTech -- the partnership behind the other mRNA vaccine that has been tailored to also target Omicron -- dictate that supply will switch to bivalent shots upon MHRA approval.
A UKHSA spokesperson declined to provide details on how much supply the country has of the Moderna bivalent shot.
"Where feasible, it would be preferable for a single type of booster vaccine to be offered throughout the duration of the autumn programme for simplicity of deployment," the JCVI said in a statement on Monday.
At the same time, the JCVI also advised that the original Moderna vaccine, the original Pfizer-BioNTech vaccine, and the Novavax shot -- for certain patients -- can be used in the autumn booster campaign.
"It is important that everyone who is eligible takes up a booster this autumn, whichever vaccine is on offer," Wei Shen Lim, chair of Covid-19 immunisation on the JCVI, said in a statement.
Lost momentum
While the original Covid-19 vaccines continue to provide good protection against hospitalisation and death, vaccines have become less effective as the virus has evolved.
Britain was the first to approve Covid vaccinations in 2020, but has since lost momentum and is now in such a vulnerable position "any booster programme is to be warmly welcomed," Danny Altmann, professor of immunology at Imperial College, London, told reporters.
The debate about the nuances of which booster is tricky -- the bivalent booster may offer some additional benefit against the BA.5 variant now dominant in Britain, although this may not be substantial, Altmann said.
"Still, the benefit coming into a difficult winter will be palpable if we can really encourage large-scale uptake," he added.
In the week ending August 5, more than 800 deaths were registered within 28 days of a positive Covid test in England, data published by the government showed.
