Canada on Friday authorized a fourth Covid-19 vaccine, adding Johnson & Johnson to its approved list alongside AstraZeneca, Pfizer-BioNTech and Moderna shots.

It is the first single-dose Covid-19 vaccine to be authorized in the country, and has been cleared for use by people over 18 years of age. 

Ottawa has ordered up to 38 million doses, which can be stored at refrigerated temperatures from two to eight degrees Celsius (35-46 Fahrenheit), making distribution easier than some others.

"We concluded that there was strong evidence that showed that the benefits of this vaccine outweigh the potential risk," Health Canada chief medical officer Supriya Sharma told a news conference, adding that its evaluation will continue as it is rolled out.

All of the vaccines approved for use in Canada so far "are effective against severe cases and hospitalization," she added.

In total, Ottawa has ordered or reserved more than 400 million doses of vaccine from seven suppliers for a population of 38 million.

Health officials are expected to announce in the coming weeks a decision on Novovax's vaccine candidate -- the only other one to have submitted an application for approval to date.

As of Friday, Canada has reported more than 878,000 cases of the coronavirus and over 22,000 fatalities.