COVID-19 Data For My Neighborhood as of March 1, 2021

If you live on the west side of Los Angeles, this article might help you understand the prevalence of COVID-19 cases in your neighborhood.

See the article introducing this series for an explanation of the data presented here.

LA County Deaths and 10-day Rolling Sum of Diagnosed Cases

Here is the plot showing daily deaths (red line) and the 10-day rolling sum of daily cases (blue line). The large spike in the plot of daily deaths is a result of adjustments to reporting. Here is the tweet from the LA County Department of Public Health explaining the situation.

“Through extensive checks of death records, Public Health identified an additional 806 COVID-19-related deaths that were not initially recorded as COVID-19 deaths. The majority of these deaths occurred during the surge between December 3rd, 2020 and February 3rd, 2021, a period when many deaths occurred and not all were reported to Public Health due to the volume of records. These deaths are reflected in the total number of deaths listed.

806 deaths over a period of about 60 days is an average of over 13 deaths per day over and above the heavy red line (7-day rolling average) in the plot below. Because it is a rolling average, the adjustment will fall out of the rolling average in a few more days. That is, the spike in the plot will drop back to its previous downward trend.

The events, arrows, and lines on the plot continue to tell a consistent story. Referring to the letter on the lower plot:

[C] Three weeks after the start of relaxed restrictions in Los Angeles, the 10-day rolling sum of cases halted its decline for a few days. Fortunately, it appears to be trending down over the last few days, perhaps indicating that the relaxation in restrictions will not lead to a surge in cases. The 10-day rolling sum of new cases has fallen to close to its lowest levels during the early fall.

10-day Rolling Sum of Diagnosed Cases in My Local Area

Here is the plot showing the 10-day rolling sum of cases for communities of interest to me. The trend across all communities continues downward.

Daily Rate of Diagnosed Cases per 100,000 Population for My Local Area

Here is the plot of the daily rate per 100,000 for communities of interest to me. This plot covers the last 60 days. Malibu + Palisades and Santa Monica are both trending downwards.

Community Immunity

In previous articles, I discussed the factors affecting the overall immunity for a population. To recap:

1. The number of positive diagnoses from testing does not measure the actual number of infections in the population. Estimates of the under-diagnosis range between 1 in 2 to 1 in 5, meaning, for example, testing only identifies 1 out of 5 or 20% of the actual infections. Early in the pandemic, under-diagnosis could have been as high as 1 in 10 or 1 in 25, at least partly because of the limited number of tests available.
2. The number of people with immunity to the virus is a combination of those who have previously been infected and those who have been vaccinated. Because testing does not detect all of the actual cases, some vaccine doses are given to people who have already been infected and thus do not contribute to increasing the pool of people who are immune.

An article appeared on the Wall Street Journal web site recently, written by Dr. Makary, a professor at the Johns Hopkins School of Medicine and Bloomberg School of Public Health. In it, Dr. Makary specifically addressed the combination of the two factors: immunity from having been previously infected and immunity gained via vaccination. It ends with a provocative assertion by Dr. Makary,

“Some medical experts privately agreed with my prediction that there may be very little Covid-19 by April but suggested that I not talk publicly about herd immunity because people might become complacent and fail to take precautions or might decline the vaccine. But scientists shouldn’t try to manipulate the public by hiding the truth. As we encourage everyone to get a vaccine, we also need to reopen schools and society to limit the damage of closures and prolonged isolation. Contingency planning for an open economy by April can deliver hope to those in despair and to those who have made large personal sacrifices.

When institutions attempt to manipulate the public by hiding the truth, no matter how well-meaning, the bad outcome they were hoping to avoid becomes a self-fulfilling prophecy because hiding the truth results in public mistrust in those institutions. I certainly do not believe there is any conspiracy to prevent people like Dr. Makary from stating their opinion. On the other hand, there is a large gap between one doctor’s opinion and public health policy.

In addition, there is room for differences of opinion whenever someone attempts to predict the future. In response to Dr. Makary, Dr. Scott Gottlieb offered some perspective.

Gottlieb said he does not “necessarily agree” with some of the numbers Makary used to undergird his argument but added, “I think the sentiment is right.”

Given uncertainty over public acceptance of vaccinations and the potential for virus mutations, Dr. Makary’s prediction of, “very little Covid-19 by April” seems optimistic for the US as a whole. But LA County has had a high rate of COVID-19. Do the number shed any light?

As you might expect, it is a difficult question to answer. I have made several very large assumptions to get even an inkling of the levels of immunity in the population over the next few months. As a result, I wouldn’t call this a prediction but rather an exploration of the range of futures that might come to pass.

First the assumptions:

1. I assume the current rate of vaccination stays the same as it has been over the last two weeks. There is a very good chance the rate of vaccination will increase in the coming months, leading to higher levels of immunity than my model shows.
2. I assume the current rate of infection (the number of daily cases) stays the same as it has been over the last two weeks. The current rate is trending down and as more people receive vaccinations, there will be fewer people available to be infected, resulting in fewer new cases. This leads to lower levels of immunity than my model shows.

These assumptions tend to offset one another though to what extent it is impossible to say. The plot below shows the results for three under-diagnosis scenarios, 1 in 2; 1 in 4; and 1 in 5.

If testing identifies 1 in 5 actual cases (gold bars), then LA County could reach 80% immunity by the end of April; 90% immunity by the end of June. If testing identifies 1 in 4 actual cases (green bars), then LA County could reach 80% immunity in June; 90% in August. If testing identifies 1 in 2 actual cases (blue bars), it will take until the end of August to reach 80% immunity; October for 90%.

Being rational and responsible individuals, I am sure none of my readers will take any of this as permission or motivation to avoid vaccination or to throw all pandemic precautions to the wind. I certainly don’t. But as Dr. Makary suggests, it offers hope.