Coronavirus: What's happening in Canada and around the world on Monday

The latest:

Long lines formed at vaccination centres in Britain as people heeded the government's call for all adults to get booster shots to protect against the omicron variant of the coronavirus, which the prime minister said Monday has caused at least one death.

In a televised announcement late Sunday, Prime Minister Boris Johnson said everyone 18 and up would be offered a third vaccine dose by Dec. 31 — less than three weeks away, and a month earlier than the previous target.

"We are now facing an emergency in our battle with the new variant, omicron," Johnson said. He said boosters would "reinforce our wall of vaccine protection" against an anticipated "tidal wave of omicron."

U.K. health authorities say omicron cases are doubling every two to three days in Britain, and it will replace delta as the dominant strain within days. But it's unclear whether the expected wave of infections will inundate the country's health system.

About 10 people are in U.K. hospitals with COVID-19 caused by omicron, and Johnson on Monday reported the country's first COVID-19 death involving the variant.

Scientists in South Africa, where omicron was first identified, say they see signs the variant may cause less severe disease than delta but cautioned it was too soon to be certain. Health authorities around the world are watching Britain closely to see what an omicron surge looks like in a country with an older, more highly vaccinated population than South Africa's.

More than 80 per cent of people age 12 and up in Britain have received two vaccine doses, and 40 per cent of adults have had three. Giving the rest boosters by the end of the month will be a huge challenge, requiring almost one million doses administered a day. Johnson acknowledged that many routine medical procedures would have to be postponed to meet the goal.

Teams of military planners and thousands of volunteer vaccinators will help give the jabs at doctors' offices, hospitals, pharmacies and pop-up vaccination centres.

While the online appointment booking system will not be open to under-30s until Wednesday, Johnson said any adult could show up at a walk-in centre to get a booster starting Monday.

Lines built up at big London vaccination clinics on Monday morning. The line for shots at St. Thomas's hospital, on the south bank of the River Thames in London, stretched across Westminster Bridge toward Parliament.

The government's appointment-booking website struggled to keep up with demand. The National Health Service advised people to try accessing the site later in the day or on Tuesday, if they were having problems.

The government also ran out of rapid at-home virus test kits, which have been distributed free to households during the pandemic. The website where tests can be ordered said none were available on Monday. Starting Wednesday, people in England must show proof of vaccination or a negative test to enter nightclubs and other crowded venues.

Johnson's Dec. 31 target applies to England. The other parts of the U.K. — Scotland, Wales and Northern Ireland — are also expected to speed up their vaccination campaigns.