The Centres for Disease Control and Prevention (CDC) is expected to reverse the relaxation of guidance surrounding mask-wearing for vaccinated Americans indoors in some areas, reports have said.

       The New York Times reported that the agency is expected to make the recommendation as early as Tuesday with CNN reporting that officials took into consideration new data surrounding the Delta variant on Sunday night.

       In May, the CDC relaxed mask-wearing guidance for those who had been fully vaccinated against coronavirus, saying they did not need to wear them outdoors in crowds and in most indoor settings.

       The guidance did not apply to those who had not received vaccinations, who were advised to continue wearing masks indoors.

       “Anyone who is fully vaccinated can participate in indoor and outdoor activities -– large or small — without wearing a mask or physically distancing,” Rochelle Walensky, director of the CDC, said at the time.

       “If you are fully vaccinated, you can start doing the things that you had stopped doing because of the pandemic.”

       While the US has seen a large decrease in coronavirus cases across the nation in recent weeks, the more transmissible Delta variant is causing a localised surge in infections.

       Over 49 per cent or 163 million people across the US have been fully vaccinated against coronavirus since the mass vaccination programme was rolled out in December.

       Although coronavirus vaccines can greatly reduce an individual’s chance of infection or serious illness, they are not 100 per cent effective.

       Health officials have urged Americans to get their shots, saying vaccines are still the best method of defence against the disease.

       The state Department of Public Health has said that 99 per cent of cases between 1 January and last week were among those who haven’t been vaccinated.

       The Independent has contacted the CDC for comment.