French biotech firm Valneva has said its Covid-19 vaccine candidate was efficient as a booster for people who had received the same shot as an initial vaccination.

“Initial results confirm that VLA2001 significantly boosted immunity in participants who received VLA2001 as a primary vaccination,” it said in a statement.

The news comes almost two weeks after a British study showed VLA2001 was the only shot out of seven that offered no immunity boost when given to people previously immunised with Pfizer's Covid-19 vaccine, AFP reported.

Valneva had said in reaction to that study that participants had been given booster doses after a shorter interval than usual and that vaccines made from inactivated viruses, such as its candidate, typically require longer to be effective.