MONTREAL, Canada - Canada's health authority said Monday it has approved Pfizer's anti-Covid pill, Paxlovid, for adults at high risk of progressing to serious disease.

The oral treatment was approved after an "expedited review," Health Canada said in a statement on its website, adding that it would continue to monitor its safety and effectiveness.

"No drug, including PAXLOVID TM, is a substitute for vaccination," the statement added.

The drug, which comprises two types of tablet, is the first Covid-19 therapy which can be taken at home, and is potentially a huge step towards ending the pandemic.

"Today's announcement is particularly important as access to easy-to-use treatments could help to reduce the severity of Covid-19 in adults who become newly infected and are at high-risk of progressing to serious illness," said Theresa Tam, Canada's chief public health officer.

The approval comes as Canada, like many countries, has been struggling to contain the Omicron variant of Covid-19.

The French-speaking province of Quebec recently announced it would levy a tax on the unvaccinated, arguing they impose a burden on everyone else.

Paxlovid has so far been authorized in a handful of countries including the United States and Israel, while the European Union has allowed member states to use it ahead of formal approval as an emergency measure against Omicron.

Unlike vaccines, it does not target the ever-evolving spike protein which the coronavirus uses to invade cells.

It should therefore in theory be more variant-proof, and the company has said preliminary lab studies have backed up that hypothesis.