One clear pattern from the first 18 months of coronavirus is that each apparent certainty is overtaken by events. The latest is that the west — chiefly, the US and western Europe — is moving to post-pandemic normality. That is far from assured. As vaccination rates taper off, the goal of reaching herd immunity is bumping up against the cultural resisters. Two steps forward are followed by one back. The concern is that new mutations will outpace the west’s ability to inoculate its laggards.

They have already caused President Joe Biden to miss his goal of 70 per cent vaccination by July 4 — the first self-imposed target he will have flunked. The White House says it will be met a few weeks later. But that could require steps Biden and the states have so far avoided for fear of inflaming the culture wars, such as mandating students to get their shots before going back to school. Similar difficulties await most European countries. The slow ones are catching up with the early adopters partly because the latter are reaching a plateau.

The risk that the west will be forced into another winter shutdown should not be downplayed. Governments face two big challenges. The first is to navigate the age-old battle between freedom and security. Almost every western nation, not just the English-speaking ones, has opted for persuasion over coercion. Lottery tickets and free beer work better than imposing fines on the hesitant. But the rollout’s early successes are sapping momentum to win over society’s holdouts — the young, the religious and various marginalised groups.

The US faces a growing free-rider problem. As social distancing evaporates, so does the incentive to vaccinate. More than anywhere else, Americans have embraced the idea that the pandemic is over. Sports stadiums are nearing capacity. Indoor restaurants are teeming. Masks are seen as elitist in much of the country. Some of this stems from the Center for Disease Control’s rash declaration in May that only the unvaccinated need mask up indoors. America’s cultural divisions are bad terrain for such an honour system, especially when vaccine certificates are so easy to forge.

Plummeting death rates further reduce America’s sense of urgency. The Delta variant first detected in India may be far more contagious than its predecessors. But the west’s leading vaccines have so far proved effective at keeping hospitalisation rates down. Britain is now dominated by Delta but its death toll has barely increased. This is great news. Yet the virus’s history suggests this could be one stage in a longer mutative journey. Getting to 70 per cent inoculation looks do-able in most western countries. Reaching 85 per cent is ambitious — and probably beyond America’s reach.

Compared with that hill, however, the rest of the world looks Himalayan. Biden and his G7 counterparts won applause earlier this month for their global pledge of 870m vaccine shots. That is far better than nothing. But they are too few and their distribution will take too long. Only half of America’s 500m pledge will be distributed this year. The west has thus undertaken to cover far less than a fifth of the world’s 11bn demand. China and Russia will probably add at least as much with their vaccines, although at lower rates of effectiveness. This is both a missed geopolitical opportunity for the west and a viral risk to its citizens.

The cost-benefit analysis is hard to grasp. IMF experts estimate that it would cost $50bn to inoculate most of the world by mid-2022. The west has a once in a generation chance to stamp its brand on global wellbeing. In February, Biden signed a $1.9tn stimulus that drew criticism from many economists as unnecessarily large. For barely 3 per cent of that, the west could win the gratitude of billions. In football terms, Biden is standing before an open goal. Supply constraints would quickly ease if global vaccination were made a priority.

Politics explains most of the west’s hesitation. Leaders fear the populist attacks that would greet large subsidies to foreigners. Yet such caution also carries risks. The Delta variant already accounts for a third of new US infections, and is growing in continental Europe. Should new variants follow, another winter lockdown would loom. Good luck seeking re-election in those circumstances. Western democracies then would no longer seem quite so prudent.