We have come full circle in one year’s time – COVID-19 mortality rates for the last week of March 2021 are identical to those of the last week of March 2020, 0.1 daily deaths per 100,000 population (Figure 1). It took a lot of work to arrive back where we started.
In general, mortality rates have tracked with case rates throughout the entire pandemic (Figure 2 below) – with a slight 2-3 week delay. In other words, as cases begin to rise, soon thereafter deaths begin to rise Lending visual credence to the “more cases, more hospitalizations, more deaths” adage we have experienced since the earliest outbreaks in Italy, for example.
A couple of trends are notable looking at these two juxtaposed graphs (plotted on a log scale so they can be compared directly – note that this will smooth out some of the peaks most particularly in mid-summer). But what we can see is that deaths rise swiftly in the early days of the pandemic, quickly reaching a peak of 0.4 daily deaths per 100,000 that holds as a maximum until after Thanksgiving 2020. So why did they rise so quickly and then flatten? Well, initially we had no idea what we were doing – no idea that individuals did better if we delayed placing them on ventilators or if we started steroids earlier. By that point there were no monoclonal antibodies and, from a public health standpoint, we were only learning that older individuals were at greatest risk. All of those factors combined to create a harsh initial reality and high mortality rate.
By December, however, we had completely overwhelmed our healthcare system with cases which had been rising since September but then jumped with Thanksgiving travel (note Los Angeles County put in travel restrictions after Thanksgiving but should have done so beforehand). So our early September ratio of 7.8 new daily cases per 100,000 to 0.2 daily deaths became 140 / 2.7 at our January peak. In fact, our mortality rate ratio (cases:deaths) went from 39 to 52 again likely indicative of an overwhelmed system.
But look at the two curves after January – we can now see a bit of a plateau in case rates over the last month, but death rates have still dropped sharply nearly approaching zero. While a less punished healthcare system and better treatments are no doubt part of this trend, consider too the potential effect of vaccinations which began in earnest in January among our most vulnerable. With 100% effectiveness against hospitalization and deaths, we may indeed be seeing the efficacy of these vaccines (primarily Pfizer and Moderna) in action.
See – not all doom and gloom from this writer.
Acknowledgements: thanks to @tdubey from Twitter for pointing out the contribution of vaccination (even just first doses) on the mortality rate curve