COVID-19 Data For My Neighborhood as of April 26, 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) for LA County.

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

[E] There is, as yet, no evidence of a surge in cases following the transition from Red to Orange Tier. That transition is now three weeks in the past and assuming previous patterns hold, the likelihood of a surge is low. In my mind, the biggest difference between now and six months ago when the winter surge started, is widespread vaccination, combined with a significant number of people who are immune after having contracted the virus and recovered.

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. It appears as if cases in the local communities are finally declining to pre-surge levels.

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.

This plot provides additional evidence that the vaccination program in LA County has been effective. Even with relaxed restrictions on public gatherings, the rate at which new cases are diagnosed has steadily declined.

Community Immunity

In previous weeks, I have tried to estimate or at least provide bounds for the level of immunity in the local population. I have covered the uncertainties in this estimate in previous reports. This week, I’d like to try a simpler approach.

Here is the plot showing the sum of vaccinations and positive test diagnoses as a percent of population in the communities of interest to me. This data is as of April 18, 2021.

I consider this to be a lower bound on the level of immunity in the local communities. In other words, the actual level of immunity could be higher, but is unlikely to be lower.

As discussed previously, the notion of “herd immunity” is appealing but it is very difficult to pin down exact numbers. Broadly speaking, if the transmission rate of the virus is relatively low (either naturally or because people take prophylactic measures) then the level of immunity in a population needed to prevent widespread infection is lower. The Mayo Clinic did not offer a specific number but suggested the number could be 70%. WebMD is more optimistic, suggesting the number could be 50% to 67%. Johns Hopkins Bloomberg School of Public Health also offers the 70% number but ultimately settles on “a large majority of the population.” All of these articles make clear the situation is complicated and many factors could influence the future course of the pandemic. But I think it is safe to say, we here in the local communities, and in LA County as a whole are rapidly reducing the probability of another surge, even as more and more public interaction is allowed. And if you have already been vaccinated, in addition to reducing the chance of infection and reducing the chance of a fatal outcome, your risk of encountering the virus in public is rapidly decreasing.