First, here is my latest radio interview, about 20 minutes long: COVID, By the Numbers (virginiainstitute.org)
As predicted, COVID is in rapid decline nearly everywhere. Since the national peak on January 11, active US COVID cases have declined by over 40%. Most of this decline is the natural course of the disease, but from this point on vaccinations will dominate the decline. I’m still modeling that we need less than 100 million vaccinated to reach herd immunity, and far less than that to influence the numbers. As of today, 26 million people are reported to have had one or more doses in the United States – with reporting lags, the true number is likely around 30 million. Many experts say we need 75% or more of the population vaccinated to reach herd immunity, or about 250 million.
Why do I think the number is so much less? Let’s start with how many people have had COVID. The official number reported as of yesterday is 25.8 million, but we know that reported cases are a fraction of those that have actually been infected. Serum studies back in the spring and summer suggest that anywhere from 10 to 50 times the reported number actually were infected. I believe that this multiple is much lower now with more ubiquitous testing. In fact, based on my mortality calculations in the spring, I triangulate that the current ratio is about 3.6. In other words, 25.8 million people have tested positive for COVID since the beginning, but more like 93 million have actually been infected. Since the ratio was certainly higher in the beginning, I’ll round up and call it an even 100 million – it could be more.
In addition to this, I believe that a substantial portion of the population has innate resistance to the disease. Those that have studied this estimate that somewhere between 20 and 50% of the population has some level of immunity due to T-Cell cross-reactivity with other viruses (for more on this read here: https://www.cnn.com/2020/08/02/health/gupta-coronavirus-t-cell-cross-reactivity-immunity-wellness/index.html) If we assume the mid-point, that would suggest that 35% of the U.S. population has some level of built-in resistance to COVID. That would be another 116 million people.
I picture it like this:
The grey area represents those that are still susceptible to COVID, about 35% of the population. I’m assuming that the balance (65% of the population) now have some level of immunity, not including any of the recently vaccinated population. To get this number up to 75% — the range of herd immunity – we require that 33 million of the susceptible group be vaccinated. Of course, vaccines are not given only to those susceptible, but more evenly distributed across the 3 groups. Assuming an even distribution of vaccines, we require about 94 million vaccinated to get the job done. It would be less if we put those that had COVID later in the vaccination process, but I don’t think anyone is talking about that. In any event, it won’t take nearly as many vaccines as you’ve heard to make a serious dent in the COVID numbers.
Of course, these estimates are rough – we don’t have anything better to go on, but I think I’m in the ballpark. Also realize that I’m making three major assumptions here:
- That those that have had COVID are substantially immune in the short term
- That the vaccines are effective in preventing COVID
- That a substantial portion of the population carries innate resistance to COVID
As far as the first assumption, I realize that there are reports of people contracting COVID more than once, but so far these are anecdotal reports and not statistically significant. The second assumption does not seem to be controversial, and the third I have written about over the past 6 months regularly. I continue to believe it based on the testing evidence and how well it explains the math. In any event, we’ll know soon enough…
Here is where we stand with known active cases. We are back down to the level we saw in the first half of November, with less than 1 million known active cases. It wouldn’t surprise me to see a leveling of this curve over the next 2 weeks, but by mid-month the vaccination process will be the controlling factor.
Below is the national daily death count. The brown line is my projection or peak daily deaths, which has been tracking pretty well. I expect peak daily deaths today or tomorrow, and then steady declines.
Here is the graph of daily deaths per 1,000 known active cases, still remarkably stable, and a good predicter of daily deaths over the next 3 weeks.
All of the states I track are in general decline, with some receding faster than others, but all going in the same direction (with the exception of NJ). Here is Arizona, with significant declines over the past 20 days.
SC is now in general decline.
Here is Florida – down sharply since the peak on January 8th. Now back to mid-July levels.
California is back to where they were in early December.
Georgia peaked 19 days ago, and has fallen steadily since.
Same caveats with Texas as always – their reporting is messy, but nonetheless declining for 21 days.
Here are VA and NC. Big drop in NC, and a smaller decline in VA.
Washington data is a mess. I won’t bore you with the details, as I have in previous reports, but here is what it looks like.
Here are NY and NJ – NY declining nicely, but NJ relatively flat for nearly 2 months. This one is a mystery to me. It could be a function of the extremely high population density.
Here is Massachusetts. Familiar pattern.
…And here is Michigan, back down to October 2020 levels.
Here is PA with a general downward trend since mid-December.
Here is Colorado – also back down to October 2020 levels… They are down 75% from their peak.
Here is Illinois, similar to Colorado – dramatic decrease beginning mid-November.
Here is Wisconsin, same pattern. Here back to September levels.
Here is Alabama. In general decline for 20 days.
And Tennessee… dramatic decline from the peak.
Here is Ohio – big declines since mid-December, then a smaller climb in January, and now down again.
Here is Indiana, following our now familiar pattern.
And finally, here is South Dakota, with just a bit over 1,000 cases left. This will likely be my last report on SC, as the numbers are not significant nationally, or even in contrast to the SD population…
So that’s it for today. I’ll report again in a week or two, I expect with more good news.
–Shane Chalke, FSA