Paxlovid, a Pfizer's coronavirus disease (COVID-19) pill, is seen manufactured in Ascoli, Italy, in this undated handout photo obtained by Reuters on November 16, 2021. (Photo: REUTERS)

The deal is roughly twice the size of the contract the US government has with Merck although the price for the Pfizer pill is lower at roughly 530 USD per course compared with about 700 USD for Merck's.

Pfizer applied for emergency authorization of the drug, branded as Paxlovid, this week after reporting data showing that it was 89% effective at preventing hospitalization or death in at-risk people.

Pfizer said it would begin deliveries of the treatment as soon as this year if it is authorized by the US FDA.

Getting vaccinated should still be the priority for Americans but having pills that can keep people out of the hospital "could be a lifesaver", said the Department of Health and Human Services.