Ms Greer McVay insists she is "not an anti-vaxxer - not at all". She is up to date with her own immunisations and had her son vaccinated when he was a child. But she fears the development of a vaccine for coronavirus is being dangerously rushed, in part to improve United States President Donald Trump's prospects ahead of the presidential election in November.

"This situation is different because of the politics that have been injected into the process and the speed at which they're developing the vaccines," says Ms McVay, a communications consultant from California and a supporter of the Democratic Party. "Frankly, I don't trust this president. It just gives me pause."