Canada has finally reopened its border to American citizens and permanent residents – but only to those who can prove they have been fully vaccinated against Covid-19.

       Those entering the country must send an application via an app and provide a negative Covid test from the three days before their intended crossing. The US-Canada border is among the world’s busiest for both tourism and commerce, and the financial boost to businesses on the Canadian side will be substantial.

       The US, however, recently extended its ban on non-essential travel from both Canada and Mexico, though American citizens and permanent residents returning from trips north will not be subject to such stringent requirements. Other American restrictions on travel from particular countries remain in place, and the Biden administration is under particular pressure to open certain routes – including between the US and the UK, which opened its borders to vaccinated Americans at the start of August.

       The Canadian opening comes as travel within the US itself becomes a matter of concern. The Delta variant of Covid-19 is spreading fast, in particular in areas lagging behind in vaccination numbers – among them Florida, whose Republican governor, Ron DeSantis, has fought against local efforts to bring in mask mandates and sold T-shirts reading “Don’t Fauci My Florida”. The state recently broke its own daily record for new Covid cases three times in a week.

       Because the proportion of people vaccinated varies substantially across the country, intra-US travel is becoming a major point of concern. Some mass gatherings that draw crowds from across the country have already been cancelled. Among the casualties is New Orleans’s Jazz Fest, whose organisers said they were scrapping this year’s festival because of the “current exponential growth of new COVID cases in New Orleans and the region and the ongoing public health emergency”.

       However, some large events are going ahead, among them the Sturgis Motorcycle Rally in South Dakota, which is expected to attract as many as 700,000 people. Last year’s event drew furious criticism for gathering massive crowds at the height of the pandemic, though one academic study that blamed it for more than 200,000 cases across the US was widely criticised for its methodology.