COVID19: How are we doing?

Note: The following is somewhat different from my usual blog posts because it doesn’t involve internet data. It’s my analysis of publicly available health data which I did to answer a question I had.

The current phase of the COVID19 pandemic is affected by several trends which are driving the pandemic in opposing directions. One the one hand, the vaccination rate is high in many developed countries. On the other, new strains such as the Delta strain are more infective and the vaccines are thought to be less effective against these strains (even though they are still highly effective!).

What is the overall trend?

Scotland may be a good area to examine this question. On the one hand, at the time of writing 54% of the population has received two vaccine doses (73% received only one). On the other, since mid-May 2021 the delta vaccine is the dominant strain in Scotland.

Here is a plot of four indicators (source) of the pandemic: Number of daily positive cases, hospital admissions, ICU admissions and deaths. They are smoothed using a 7-day moving average. 

Four indicators of the COVID19 pandemic in Scotland

On average, hospital and ICU admissions are best correlated with daily cases when those are taken 7 days later (that is, it takes around a week until a case is hospitalized), and another 7 days until deaths occur.

Therefore, I used the daily positive data to predict both hospital admissions and deaths at the appropriate lag (7 and 14 days). In both cases I used a non-linear model (second order polynomial to predict the quadratic root of the dependent variables) trained on data until the end of April 2021. The models had a good fit (R2=0.69 and 0.52, respectively).  

Here are the actual and predicted hospitalizations, compared to case numbers:

Daily positive cases, hospital admissions and predicted hospital admissions

As we can see, hospital admissions are rising since mid-May, but not as fast as the prediction. We would expect around 170 people to be hospitalized at this point, but there are around 45. That’s around one quarter of the expected number.   

A look at deaths is even more telling:

Daily positive cases, deaths and predicted deaths

Deaths have risen very slightly: We would have expected almost 40 per day at this stage, but are seeing around 2 (that’s one twentieth of the expected!).

My takeaway from this is that we will see a rise in hospitalizations and in deaths, but it will be much smaller than in previous waves of COVID19, especially in terms of deaths. The vaccines are providing significant protection against the worst aspects of COVID19.

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