Way back in February — back when the US had 13 COVID-19 cases, and not 4.8 million — Donald Trump said that one day soon the virus would just "go away.

"We're going to have vaccines very soon," Trump said today on a radio show, for at least the third time this week.

Today, Trump said the vaccine could come "sooner than the end of the year," maybe even sooner than the November 3 election.

But with all the grasping around at "when", the conversation barely grazes over "whether" — as in, whether a vaccine could ever really make America's mess, as Trump put it, "disappear".

Initial doubt around vaccine efficacy has faded as scientists continue to study COVID-19.

As nations race to be the first to get a vaccine to market, there's no reason to believe the US lacks the money and power to get its hands on one eventually.

But most of the top vaccine contenders rely on scientific methods that have never been carried out on a large scale before, which leaves experts thinking missteps are inevitable.

Even while promising a vaccine is just around the corner, the Trump administration has released very little — and often very confusing — information about roll-out plans.

Current vaccine infrastructure is designed for children, not adults, and couldn't be quickly adopted without the Trump administration stepping in.

Twenty per cent of Americans say they plan to refuse a COVID-19 vaccine.

Among black Americans, who account for roughly a quarter of US COVID-19 deaths, roughly 40 per cent say they won't get a vaccine.

But for another group of Americans, the vaccine fuels a sense that all the patience will have been worth it.