Health Canada has approved the use of Pfizer’s antiviral pill treatment for COVID-19.

The federal health agency says the prescription-only medication, dubbed Paxlovid, can be given to adults ages 18 who have mild to moderate cases of COVID-19 and are at a high risk of becoming more seriously ill. 

The decision comes as COVID-19 cases and hospitalizations have been surging in Canada due to the Omicron variant, forcing provinces to re-enter lockdowns.

The authorization, posted on Health Canada’s site this morning, specifies scenarios in which the drug cannot be administered, including to prevent COVID-19 infections or to treat patients who are already hospitalized due to severe COVID-19 cases. The medication can’t be taken for longer than five days in a row, and isn’t greenlit for use on teens or children.

According to Pfizer, Paxlovid uses a combination of drugs to prevent the virus that causes COVID-19 from replicating itself once it’s infected a patient. Part of the pill uses ritonavir, a drug that’s been used in combination with other antiviral medications before.

Clinical trials show that there was an 89 percent reduction in the risk of being hospitalized or dying of COVID-19 in patients who received Paxlovid within three days of showing symptoms of the virus, compared to the study group that received a placebo.