This was originally a Facebook post of mine from 2021-4-2, and is archived here as a curiosity. Minor changes to formatting, as well as basic copy-edits, may have been made in the transition from Facebook post to web format.
The news about the virus, in the US, is mostly good this week, despite the slight increase in cases and new hospital admissions. Three main ideas: (1) cases and hospitalizations are continuing to rise a bit, (2) deaths are dropping nicely, and (3) the vaccine rollout is going better than ever this week.
(1) Cases and hospitalizations
EDIT (4/3/21): The math in this section, and at the end, skipped a step, coming up with the figure of 24 million where it now reads 16 million.
Two weeks ago today, the seven-day rolling average of cases was 53,114. One week ago, it was about 58,706. This week, 63,727. Or, in other words, a 10.5% rise in cases the one week, and 8.6% the next. And a little rough math suggests that, all other things being equal, another 16 million vaccinations would be enough to make cases start heading back down again. That's a rough number, because there's all sorts of variables going on, but it's a reasonable guess. The math is at the end of the post, after "sources". At the rate things are going, 16 million new vaccinations would take about 10 days, so most experts expect to see the number of cases declining by a few weeks from now.
New hospital admissions averaged 4,969 over the last week, up from 4,761 the week before. So far, the rise in hospitalizations has been gentler than the rise in cases. This makes sense -- the population of people catching Covid has been getting younger, since about 75% of people over 65 have been vaccinated.
(2) Deaths are dropping
Over the last seven days, an average of 858 people have died of coronavirus, down from 963 the week before. This is progress. In a particularly bad flu season, about 650 people die per day. So as we continue to move toward putting the virus behind us, we are likely to soon be in a situation that's like a bad flu year.
(3) The vaccine rollout
The daily number of vaccine doses given per day continues to increase. The last week had the highest average yet, at 2.99 million doses per day. I was one of them. Each day, about 1.6 million people are getting their first dose -- that's about 11 million people per week.
So far, 102 million people have received their first dose. Recent polling suggests that about 80% of Americans now say they have been or most likely will get vaccinated. That comes to about 204 million adults, so 102 million left to go. We're exactly half-way through the process of getting everyone their first shot, give or take a normal polling error. And at 11 million doses per week, that leaves about 9 weeks worth of vaccinating to get a shot to everyone who wants one.
Once the vaccine has been made available to everyone who wants one, there is no politically viable path to continuing restrictions. The vaccinated people will want to go back to normal life, the unvaccinated people will want to go back to normal life, and there's no one out there with the political power to stop them.
Normalcy is coming, at a rate of three million shots a day.
Sources
For most data, CDC Covid Data Tracker.
For doses given per day, see also Bloomberg Vaccine Tracking.
For people's vaccination choice, see FiveThirtyEight.
Math
An 8.6% rise in cases per week equates to an R_t of about 1.073, assuming a six-day "generation" interval for the virus. The basic math is 1.086^(6/7) = 1.073 here. Then, in order to reduce R_t by 7.3%, you need to induce immunity in 7.3% of the currently non-vaccinated population. The basic math here is 0.073 * 228,000,000 = 16 million.
So, all other things being equal, about 16 million new people immune through vaccination would bring R_t down to one. There are all sorts of reasons this number could be too high or too low, but it's a reasonable first guess.
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