Canadian Natural (CNRL), the first oil sands company to announce such a policy, made the decision after the recent rise in infections in Alberta, spokesperson Julie Woo said. Alberta, home of the oil sands, has the highest rate of active cases among Canada's 10 provinces, with 456 per 100,000 people, according to Canadian government data.

CNRL will make exceptions from the policy for workers with verified medical or religious reasons against vaccination, Woo said.

Previously, CNRL required unvaccinated workers in the oil sands to submit to daily tests, but this will no longer be an allowable alternative to vaccination starting in December, she said.

Numerous global energy companies faced COVID-19 outbreaks last year, as oil workers tend to work in close quarters for weeks at a time.

Currently, there are outbreaks at four CNRL oil sands sites, as well as at facilities owned by Cenovus Energy, MEG Energy and Suncor Energy, according to Alberta's health ministry.

Suncor, the second-biggest Canadian crude producer, does not require mandatory vaccinations, but is expanding its policy of mandatory COVID rapid testing to most of its Suncor sites for non-vaccinated workers, said spokesman Leithan Slade. The move will begin with Canadian locations in October.

(Reporting by Rod Nickel in Winnipeg; Editing by David Gregorio)

By Rod Nickel