A booster dose of a Covid-19 vaccine candidate made by drug companies Sanofi and GlaxoSmithKline provides strong immune responses in recipients, data from clinical trials has shown.
The results released on Wednesday are expected to offer a fillip for the pharmaceutical partners, whose vaccine is lagging in the stakes behind other candidates.
Sanofi, a multinational healthcare copany with its headquarters in Paris, and GSK, with its HQ in London, said they expected more results of the late-stage Phase 3 study of their recombinant adjuvanted coronavirus vaccine candidate in the first quarter.
They plan to file booster data with regulatory authorities after the Phase 3 results.
Test results for the underlying vaccine, meanwhile, were pushed back to the first quarter. Neither study pitted the product against the new Omicron variant.
The two partners took the unusual step of saying their shot works as a booster before they could show it is effective as a first-line immunisation. More participants need to get Covid to wrap up the clinical trial, a delay that prevents the companies from seeking regulatory approval for the booster.
"The booster was well tolerated, with a safety profile similar to currently approved Covid-19 vaccines. This is the most comprehensive booster trial to date to explore boosting across different vaccine technologies used for primary vaccination", the companies said in a joint statement.
"To provide the necessary data to regulatory authorities for the booster vaccine submission, the trial will continue to accrue the number of events needed for analysis, with results expected in Q1, 2022."
No safety concerns were identified.
Sanofi and GSK have pledged to deliver 7.5 million doses of their vaccine to Britain, once it wins the approval of the medicines regulator.
So far, more than 24 million people in the UK have received a third shot of a coronavirus vaccine.
The booster shot has been tested for all age groups and for people who have received four of the most widely approved shots – AstraZeneca, Johnson & Johnson, Moderna and Pfizer/BioNTech – as part of their primary vaccine.
The shot was administered to people between four and 10 months after they received their second dose. The Omicron variant was not circulating during the trial.
"Preliminary results from the VAT0002 clinical trial investigating the safety and immunogenicity of the booster showed neutralising antibodies increased nine to 43-fold regardless of the primary vaccine received (AstraZeneca, Johnson & Johnson, Moderna, Pfizer/BioNTech) and for all age groups tested," Sanofi said.
The company said this was the most comprehensive booster trial to date as European countries grapple with a new wave of Covid infections driven by the Delta variant of the virus. Leaders across the continent imposed stricter measures as they braced for Omicron.
Sanofi also said it was continuing "its contribution to global public health needs" with the manufacturing of up to half a billion doses from BioNTech/Pfizer, Moderna, and Johnson & Johnson vaccines.
The vaccine uses the same technology as one of Sanofi's seasonal influenza vaccines coupled with an adjuvant, a substance that acts as a booster to the shot, made by GSK.
The news provides some optimism for the companies after falling behind rivals in the race for vaccines and big delays with the development of this shot.
Last year, trials for the shot showed an insufficient immune response in older people. The companies had said the vaccine could be approved by year-end after initially targeting the first half of the year.
At the end of September, Sanofi dropped its plans for its own mRNA-based Covid vaccine because of the dominance achieved by BioNTech-Pfizer and Moderna in using the technology to fight the pandemic.
