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There is a chart that is worrying that is involved in the Covid vaccine rollout here in the US. And it is this one. This shows the number of people getting shots every single day.
And until recently it was a source of great pride in the country, peaking earlier this month at an average of 3.4m doses every single day.
But look what has happened since. The number is falling just as quickly as it rose and now stands at more like 2.3m doses a day. So what's going on?
One explanation is that people have become more nervous about getting vaccinated since a handful of people encountered serious illness after getting vaccinated with the Johnson & Johnson vaccine.
And it is certainly true that the beginning of the drop-off coincides with the point at which US regulators put the J&J vaccine on pause while they investigated further.
But while confidence in J&J's particular vaccine does seem to have dropped, the overall willingness of Americans to get vaccinated does not, polls suggest.
Instead, what seems to be happening is we're simply reaching the end of the group who are most eager to get vaccinated, those people who are willing to drive for hours to do so.
Instead, the US is now trying to vaccinate people who are more cautious, who definitely don't want it at all, or simply don't see the reason to, given that they're are low risk of suffering from serious Covid effects at all.
In response, the Biden administration is trying to make it easier for people to get vaccinated.
Today, we know that many adults have not been vaccinated because they have found it too confusing, or too difficult, or too inconvenient to get a shot.
So for those having trouble finding a location or making an appointment, we're going to make it easier than ever.
It's setting up mobile vaccine clinics. It's urging pharmacies to allow people to get vaccinated without prior appointment.
And it's spending hundreds of millions of dollars on a campaign of education and outreach to make sure that people have all the information they need to make the right choice.
But some experts believe that there are now parts of the country opening up where vaccination rates are just going to be lower than other places.
And that will open up gaps for the virus to reappear, albeit, hopefully, in a much more localised and less serious way.