Vaccines are effective enough at preventing severe Covid-19 that there is no current need for the general population to be given third doses, according to a report in The Lancet published Monday.

Some countries have started offering extra doses over fears about the much more contagious Delta variant, causing the World Health Organisation to call for a moratorium on third jabs amid concerns about vaccine supplies to poorer nations, where millions have yet to receive their first jab.

But a report by scientists, including from the WHO, concluded that even with the threat of Delta, “booster doses for the general population are not appropriate at this stage in the pandemic”.

The authors, who reviewed observational studies and clinical trials, found that vaccines remain highly effective against severe symptoms of Covid-19, across all the main virus variants including Delta, although they had lower success in preventing asymptomatic disease.