Canada has discovered a total of 15 cases of the new Omicron variant of Covid-19 and severe illness trends across the country could start to rise again, public health officials said.

The federal government said it backed a recommendation of a national advisory board on immunisations that all adults above 50 should receive a booster shot six months after completion of a vaccine series, Reuters reported.

Ottawa announced last week it will require people arriving by air from all nations except the United States to take a Covid-19 test, and it expanded a ban on travellers from southern Africa to cover 10 nations.