Canada's biggest city entered lockdown on Monday in the latest bid to curb coronavirus infections, with case numbers surging across North America even as US officials said vaccinations could be available within weeks.

Encouraging results from several vaccine trials have raised hopes of a decisive shift in the battle against a disease that has claimed around 1.4 million lives worldwide in the last year.

But seesawing restrictions and lockdowns in countries that successfully contained earlier outbreaks -- shattering lives and economies in the process -- have highlighted the ongoing risk of contagion.

Toronto banned private indoor gatherings and capped the size of weddings and funerals for four weeks from midnight, with officials warning that hospitals risked being overwhelmed without quick action.

"I've been clear on this: the situation is extremely serious and further action is required," Ontario premier Doug Ford had told journalists ahead of the lockdown. 

Officials had forecast more than 400,000 new infections a week across Canada by the end of the year without new restrictions -- more than the total number of cases recorded nationwide since the start of the pandemic.

Australia's second-largest city, meanwhile, continued its slow emergence from a gruelling four-month lockdown that saw four million people confined to their homes, with authorities lifting a ban on travel across state borders.

Margaret Forster of Melbourne told national broadcaster ABC that she had been allowed to drive into New South Wales for the first time since June. 

"When I went across the border I beeped the horn, 'Yahoo!'," she said.

British media reports said Prime Minister Boris Johnson was preparing to partially ease social distancing measures in England at the beginning of next month, after concerns about the impact of lockdowns on the economy and mental health. 

And staff at Shanghai's biggest international airport were facing mass testing after the city reported a small Covid-19 outbreak linked to cargo handlers.

Life in China has largely returned to normal after strict testing and harsh lockdowns since the virus first emerged there late last year, but authorities have linked several isolated outbreaks to the import of goods. 

- Vaccine hopes - 

China has been giving experimental Covid-19 vaccines to people including state employees, international students and essential workers heading abroad since July.

The United States could begin its own vaccination program as soon as next month, raising hopes of a looming end to the pandemic in the world's worst-hit nation.

Two leading vaccine candidates -- one by Pfizer and German partner BioNTech and another by US firm Moderna -- have been shown to be 95 percent effective in trials, and Pfizer has already applied for emergency use approval from US health authorities. 

"Our plan is to be able to ship vaccines to the immunization sites within 24 hours of approval" by the US Food and Drug Administration, Moncef Slaoui, head of the US government virus vaccine effort, told CNN.

FDA vaccine advisors will meet December 10 to discuss approval.

Slaoui estimated that 20 million people across the US could be vaccinated in December, with 30 million per month after that.

But top infectious disease expert Anthony Fauci warned the country's outbreak could get worse before getting better if people failed to take precautions in the coming holiday season.

With more than 12 million cases and 255,000 deaths nationwide, many Americans were nonetheless heading to airports to travel for this week's Thanksgiving holiday.

Social distancing edicts and mask-wearing rules have spurred protests in the United States and elsewhere.

German protesters in Germany demonstrated against facemask rules in Berlin at the weekend in a rally that drew in far-left activists, conspiracy theorists and right-wing extremists who claim the measure infringes on their civil rights.

And in Paris, around 300 people attended a clandestine dance party in defiance of a national lockdown, with France now recording the highest number of Covid-19 cases in Europe.