The Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) are recommending one dose of the updated vaccine for everyone six months and older in the US; some children may be eligible for up to three doses depending on their age and previous vaccination status.
Hospitalisations and deaths from Covid-19 have been rising for weeks in the US, and global health authorities are monitoring two new variants, BA.2.86, known as Pirola, and EG.5, known as Eris.
First reported in February, Eris is now responsible for nearly 25 per cent of Covid cases in the US, per CDC data.
Doctors warned that Pirola may be cause for concern as it is a newly-designated, highly-mutated variant of Omicron which triggered a surge in cases in a number of countries including the US.
Some experts are urging Americans to wear a mask when necessary to slow the spread of the virus.
CDC Covid tracker
20,538 hospitalisations from 3 September to 9 September