"That's a long way to go given that this virus transmits very quickly," he said, adding that in Africa, "the second wave is here with a vengeance."

Only a third of the first shipment of Pfizer vaccine doses have been given across the U.S., putting the government's target for 20 million vaccinations this month in doubt.

A senior CDC official, who spoke on the condition of anonymity to preview the announcement, said the policy change has been discussed for some time.

Officials are moving to shorten the quarantine time for those potentially exposed to the virus, but experts worry not enough people are following health measures.

Jason Kenney said about 90 per cent of Albertans are already under some sort of a mask mandate, brought in by municipalities.

The CDC's update now matches recommendations from both Health Canada and the World Health Organization (WHO).

The CDC update, which references eight different studies, could be a game-changer in understanding the benefits of wearing a mask.

“There’s no invisible force field at 6 feet,” said Saskia Popescu, an infectious disease expert at George Mason University.

The CDC advises anyone who has been in close contact with a COVID-19 patient to quarantine for two weeks.

Children, who rarely have severe COVID-19 symptoms, have not yet been tested for any experimental coronavirus vaccine.