The United States has implemented the sixth-fastest vaccine distribution programme in the world, administering just over 100 million inoculations and reaching a quarter of all adults. In terms of the total number of jabs in arms, it is by far the largest rollout in the world so far.
But state and national data analysed by the Financial Times show that the rollout has been uneven, as some governors prioritise speed while others focus on vaccinating older people who are more likely to end up in hospital and die.
California, for example, has been slower than most to open up vaccine eligibility, but 66 per cent of people over 65 have received a first dose — a third more than either Texas or Tennessee.
Alaska meanwhile has overseen one of the fastest distribution programmes in the country but has given a first jab to a smaller share of its over-65 population than many other states — just 55 per cent. And it has inoculated a far larger share of people below that age: 20 per cent.
The findings underscore how the US federal government has overseen a large, rapid but disorganised rollout, with little central control over who should be vaccinated and when.
That contrasts starkly with the picture in the UK, where a similarly fast programme has resulted in nearly everyone over the age of 65 receiving at least one dose of a coronavirus vaccine.
"The UK focused entirely on bringing down hospitalisations and deaths, and so concentrated on its older population," said Dr Leana Wen, a public health professor at George Washington University.
She added: "The US has been far freer about who gets doses, but there are plus-sides to that too. If you vaccinate a younger, more mobile population, you are more likely to bring down community transmission."
After early teething problems with quality control, US vaccine production has steadily increased since it began in December.
By the end of 2020, the country was vaccinating around 300,000 people a day, according to data collated by Bloomberg. By the time Donald Trump left office in January, it was up to nearly 1 million. Now it has risen to just over 2 million.
Government officials and industry executives say two things in particular have helped make the US rollout one of the fastest in the world, despite the challenges of managing an inoculation drive in such a large country.
The first is the way in which the Trump administration spent billions of dollars early in the pandemic helping develop the vaccines, and in return secured first refusal on hundreds of millions of doses.
Charles Michel, president of the EU Council, this week accused the US of imposing a vaccine export ban, but US officials say the reality is more straightforward: America has already bought up lots of the doses.
The second factor is how closely the government has monitored the manufacturing process and the supply chain, helping spot and resolve problems before they become crippling.
Both the Trump and Biden administrations used the Korean-war era Defence Production Act to make sure vaccine makers and administrators secured priority supplies of crucial elements such as glass vials and specialist syringes.
Andy Slavitt, a senior Covid-19 adviser to US President Joe Biden, said: "We keep asking the vaccine makers, 'Do you have enough of this, do you have enough of that?' Eventually they might say: 'Actually it turns out that in three weeks' time we won't have enough people to do quality checks on packaging'."
"That's how we have been able to establish a rhythm of anticipating the problems before they occur."
But while production numbers have surged, the federal government has been able to exercise far less control over who gets the vaccine. The US Centres for Disease Control and Prevention has issued guidelines for vaccine priority groups, but states have control over their own distribution programmes and many have adapted or ignored national guidelines.
Data analysed by the FT show that while England has given at least one dose to 94 per cent of people over 65, the comparable figure in the US is around 60 per cent. According to the CDC, over-65s account for 81 per cent of all Covid-19 deaths.
Some of this can be explained by the UK's decision to extend the gap between first and second doses from three weeks to 12. Whereas 4 per cent of over-65s in England (UK-wide data are not available) have received a second dose, 29 per cent of those in the US have.
But another factor is that some states have chosen to expand eligibility more rapidly, resulting in vastly different vaccination rates for different demographics across the country.
States that have been slower to open up eligibility have sometimes been slower to get jabs into arms, but they have often been better at targeting the most vulnerable.
There are also discrepancies within the over-65 group. Florida, for instance, opened up eligibility to all over-65s on a first-come-first-served basis early in the rollout, triggering long queues at vaccination sites.
Critics said older and frailer people would be left out, and the most recent statistics appear to bear that out. Florida has vaccinated 62 per cent of people aged between 65 and 84, but only 54 per cent of over-85s.
States also vary widely in how quickly they have vaccinated black and ethnic minority populations, who are also at higher risk of dying from the virus. Data from the Kaiser Family Foundation health think-tank shows that while New Mexico has vaccinated 12 per cent of its black population, Texas has inoculated just 5 per cent.
An FT analysis last month of data from five big metropolitan areas showed people living in poorer and majority-black neighbourhoods were being vaccinated at a slower rate than richer, whiter ones.
Experts predict that the problems will not last for much longer, however, with President Joe Biden predicting enough doses for every adult by the end of May.
Dr Angela Rasmussen, a virologist at Columbia University, said: "The rollout may have been haphazard but we will overcome these state supply issues fairly soon."
© 2021 The Financial Times Ltd. All rights reserved.