Post #1130: COVID-19 trend to 5-1-2021

Posted on May 2, 2021

National trend

A little more than two weeks past the peak of the U.S. fourth wave, and the seven-day moving average of U.S. daily new COVID-19 cases is now 28% below the peak.  That’s the result of an average rate of decline of 13 percent per week.


Source for this and all other graphs of new cases:  Calculated from The New York Times. (2021). Coronavirus (Covid-19) Data in the United States. Retrieved 5/2/2021.  The NY Times U.S. tracking page can be found at

The only region without a noticeable downward trend is the Mountain region.  That’s due in large part to Colorado, which now has the second-highest rate of daily new cases in the nation.  Among all Mountain states, Colorado has a) the highest fraction of  U.K. variant cases, and b) the lowest fraction of the population immune via prior COVID-19 infection.  Meanwhile, California quietly slipped into last place, and now has the lowest new-case rate in the nation.

To my eye, the tail-end of that graph is now starting to look like a semi-coherent downslope.  We’re back to the point where, every day, the majority of states show a day-to-day decline in new cases.

U.K. variant.

As of a week ago, the more-infectious U.K. variant (B.1.1.7) accounted for more than two-thirds of new cases.  So, whatever it’s going to do to us, it’s pretty much doing it right now.

Data sourced from the Helix® COVID-19 Surveillance Dashboard. Accessed at on 5/2/2021.

Based on the five states with the highest incidence of the U.K. variant, it’s clear that the impact of the greater infectiousness of that variant is being offset, on average, by something.  Presumably, that something is the immunity via vaccination and prior COVID-19 infection.


The elderly continue to get vaccinated.  Between these last two snapshots (4/28/2021 and 5/1/2021), the fraction of the elderly who are vaccinated rose by an average of 0.2 percentage points per day.  Overall, the rate of vaccinations averaged just under three million doses per day.

Source: CDC.

You’ll note that while the rate of vaccinations appears to have peaked a couple of weeks ago, coincident with the pause in the use of the J and J vaccine, the last couple of weeks appear flat.  That is, the heights of the last two sets of bars appear similar.  So maybe that was a one-time sag in the rate, not the start of a downward trend.

Source: CDC.