Reposted from the Cliff Mass Weather Blog
I think I found something important.
But I’ll let you be the judge. And I would love to hear from epidemiologists reading my blog.
The number of COVID cases is increasing in Oregon and Washington, while the number of COVID cases is decreasing or stable in most other states. The increases are worrying enough that Governor Inslee could reverse the opening of the state.
Much has been said about the need for herd immunity where a large part of the population will be vaccinated or have had COVID so that the virus will lack enough susceptible people to spread. But nobody seems to be sure what percentage of the immune persons are needed. 60%, 80% or 90%. Some scientific articles and media reports suggest that we will never get to herd immunity. But what is the truth?
I am not an epidemiologist However, it seems to me that there should be enough information to get real answers to the above questions. And so I sat down with a cup of coffee (several, actually) and the data from the Centers for Disease Control and went nuts.
And I found something interesting.
For each state, I estimated what percentage of the population is immune to COVID-19 and then compared that to the change in the number of new cases over the past few weeks.
I found a significant relationship between the two. And I may have discovered the percentage of immunity to magical flocks.
Estimate the percentage of the population that is immune to COVID-19
First, I started with the percentage of the population of each state reported to have COVID-19, which is between roughly 4 (Oregon) and 14 (Rhode Island) percent.
There is extensive literature to suggest that the actual number of infected people is well above the official number of cases. Several research suggests that a factor of three is appropriate. So I started by taking the percentages of CDC status cases and multiplying them by 3.
Then I backed up the vaccine dates for each state and based on the CDC count of single and double vaccinations, I assigned 60% of the total vaccinations as the number of people who received at least a single shot. I then added that number to the 3x case percentages given above to get a final percentage of immune individuals for each state, with numbers ranging from .56 (Oregon) to .936 (Rhode Island). This will no doubt be a small overestimation as there will be some people who have been vaccinated with COVID, but this would only shift my herd immunity estimates by about 5-10% at most. In any case, the approach is consistent for all states.
This change in COVID cases for April 15-28
My hypothesis is that increasing percentages of antibodies to COVID should be related to a decrease in COVID case numbers. Next, I turned to the CDC COVID trending pages.
Here’s the one for Oregon. Not good. The number of cases has increased quite sharply (blue are daily values and red are 7-day eluent).
The situation is a little better for Washington State, but still in the wrong direction. Because of this, Governor Inslee is threatening a caveat (and I’ll suggest later that it would be a mistake).
On the other hand, Rhode Island and Massachusetts are seeing rapid decline. Can we understand why I think we can.
Using the CDC trend charts and their associated numbers, I found the changes in the number of cases over the past two weeks (April 15-28) using the red lines (7-day averages) for each figure. Then I compared the recent case trend trends in each state with the percentage of immune citizens. The results are shown below. And they’re exciting and make a lot of sense.
The Y-axis shows the change in the number of cases per 100,000 population, and the X-axis shows the percentage of immune citizens. Every point is a state.
The two states with the greatest increases in COVID cases over this period are Oregon and Washington! And we are the states with the lowest percentage of immune people.
However, once you are above 0.65, the COVID no longer increases significantly. What REALLY matters, however, is that the sharp decreases in the number of cases start abruptly around 0.7, with 70% of people being immune. At .7 and something very special happens it appears that it represents the transition to herd immunity.
Now you might be wondering why some states are above 0.7 but don’t show any recent changes. I think there are several reasons for this. Some of these states made the transition to herd immunity two weeks ago. As soon as a state passes, the numbers fall and stabilize. Another possibility is that a major reopening of a state can temporarily maintain the current COVID levels.
But there is a clear message from above. Once you get to .7, the expansion of COVID is over and a breakdown in the number of cases is possible.
Now there is a potential message here for Governor Inslee in all of this.
Washington State is on the verge of reaching a high enough percentage of immune individuals that COVID cases will stabilize first and then rapidly decline. Given the high vaccination rate in our state (about 60,000 per day according to the WA DOH website) and the natural spread of the virus, we’re going to move from about 0.63 today to 0.7 in about a week. Do we need to add restrictions at this point?
There are other factors that could well contribute to a sharp decline in the state of WA’s Covid numbers over the next month or so. We are now entering the warm / dry part of the year where people spend more time outside and open their windows. As mentioned in a previous blog, outside air is very COVID safe. Second, vaccinations are now available for younger people, precisely those who are a major contributor to the transmission of COVID.
Does the above analysis make sense? Why did others enter unrelated numbers? Let me know if you see any errors in logic or approach. But everything seems logical and the picture is coherent and self-consistent.