US President Joe Biden has said that he will make Covid-19 booster shots available to all American adults beginning next month, as his administration warned that vaccines are showing a declining effectiveness against infection.
The move comes as scientists and health experts grapple with how to beat back the surging Delta variant of the coronavirus, and follows extensive debate over whether a third injection of the Pfizer-BioNTech and Moderna vaccines would be appropriate.
Stressing this was "no time to let our guard down," Mr Biden urged every American aged 18 and older to get a booster eight months after becoming fully vaccinated. "This will boost your immune response, it will increase your protection from Covid-19, and it's the best way