PARIS: France's Sanofi and Britain's GSK said Friday their Covid-19 vaccines will not be ready until the end of 2021, after interim results showed a low immune response in older adults.

"Sanofi and GSK announce a delay in their adjuvanted recombinant protein-based COVID-19 vaccine programme to improve immune response in older adults," a statement said, adding that the vaccine's potential availability had been pushed back "from mid-2021 to Q4 2021".