It is late October and Donald Trump has a surprise for you. Unlike the traditional pre-election shock — involving war or imminent terrorist attack — this revelation is about hope rather than fear. The “China virus” has been defeated thanks to the ingenuity of America’s president. The US has developed a vaccine that will be available to all citizens by the end of the year. Get online and book your jab. 

It is possible Mr Trump could sway a critical slice of voters with such a declaration. The bigger danger is that he would deepen America’s mistrust of science. A recent poll found that only half of Americans definitely plan to take a coronavirus vaccine. Other polls said that between a quarter and a third of the nation would never get inoculated.

Whatever the true number, anti-vaccine campaigners are having a great pandemic — as indeed is Covid-19. At least three-quarters of the population would need to be vaccinated to reach herd immunity.