This year, Independence Day is the cue for national reckoning as well as national pride. US president Joe Biden set July 4 as the date by which 70 per cent of American adults should have a dose of Covid-19 vaccine. Official numbers suggest he will miss the mark by three or four percentage points. The winter surge in take-up has become a summer trickle.

Despair is misplaced. The US has not just outperformed most countries in the world. It has also defied the surveys in which half of its adults said they would avoid a jab. In a sense, vaccination is the ultimate audit of a country’s civic fabric: it tests citizens’ trust in authority, and consideration for each other. Given the bleak lens through which America has been analysed in recent years, this success should not be glossed over as a given.

More pressing, now, is the question of how to finish the job. The least-vaccinated states, such as Mississippi and Wyoming, are Republican-voting. The anti-elite dogma of the US right has a mortal cost. There is a limit to how much Biden or any Democrat can do here. Republicans themselves must bang the drum for vaccination. The burden falls not just on elected officials but the vastly influential ecosystem of conservative media. Israel and Britain vaccinated quickly while led by populists of a sort. US Republicans should take the cue from their ideological sister movements.

A more surprising group of refuseniks are the young. Among over-30s, Biden’s target has been met. If those below that age are holding out, it is through qualms about side effects and the natural insouciance of youth. Here, a tonal shift is due. So far, public-health campaigns have framed vaccination as a matter of what Biden calls “life and death”. The next phase calls for a subtler message. It should stress the grimness of “long Covid” (many of whose victims are young), the vulnerability of older relatives and the need for normal life to resume. No group has suffered more from the restrictions than those who would in normal times be savouring campus life, nightclubs or their first career progress. France’s acclaimed public health video on that theme is a model to emulate.

In the end, though, tangible incentives must join exhortation as part of the answer. Gifts of cash and kind — including mobile phone credits — have been tried in various places. The trickier move is to make access to travel, retail and other normalities of life ever more conditional on vaccination. The policy dilemmas here are daunting. Too crude an approach can sow rancour between citizens. Even organising proof of vaccination is difficult in a highly decentralised health system. Still, if the first wave of vaccinated people were motivated by fear of illness, the next group will probably need a positive temptation.

Last July 4, it wasn’t clear when or if there would be a vaccine. When the pharmaceutical companies delivered, it was anyone’s guess how many Americans would raise their sleeves for the shot. A vaccination rate of about 67 per cent of adults has to be seen in that context.

One lesson of this (relative) success is that leadership matters. Without access to a parallel universe, it is impossible to know the fate of vaccination under a second term of Donald Trump. In fact, it induces a shiver to even guess. But a president who scorned experts and cared little for governmental competence did not augur well. Biden is rating reasonably well as president, thanks in part to his fiscal largesse and diplomatic moves, but mostly because of his work on vaccination. His legacy, and America’s immediate future, hinges on its completion.