Hospitalisation Rate For Adult Respiratory Conditions (part 1)

Lessons from an undisclosed NHS Trust

Sometimes statisticians overlook what is plain and simple and sitting right under our noses. Today I am going to wrap split-file propensity-adjusted staged multivariate logistic regression in Clingfilm and put it back in the pantry. My stats package will be put in Tupperware and we’ll take out a fresh tub of Excel and spread it nice and simple.

We shall consider all adult (18y – 99y) admissions to the emergency department who were diagnosed with either an acute (e.g. pneumonia) or chronic (e.g. asthma) respiratory illness. We shall divide them in to those who were discharged directly back home and those who were given a bed in a short stay ward, general ward, CCU, HDU or ICU (i.e. hospitalised). We shall take a note of whether they tested positive for COVID-19 and we shall take a note of their vaccination status (unvaccinated at admission; dose 1 received prior to admission; dose 2 received prior to admission). We shall not deceive people by messing around with definitions: unvaccinated shall mean exactly that; namely no jab whatsoever at any point. If they received a dose even an hour earlier that will be counted as a vaccination.

With these definitions in mind let us look at how the various different case types were treated in terms of weekly hospitalisation rate over the period Jan – Sep 2021, starting with a slide separating non-COVID respiratory admissions from COVID respiratory admissions and ignoring vaccination status.

Interesting isn’t it? We observe a consistent trend in the hospitalisation rate for non-COVID respiratory admissions (blue line) that yields a slight decline as we move through spring to summer to autumn. This makes a great deal of sense. So what’s with the kinky COVID curve? We should note that the hospitalisation rate for COVID respiratory admissions starts out pretty similar to the non-COVID curve and yet COVID is supposed to be a more deadly disease.

We should also note that the hospitalisation rate for this more-deadly-than-normal disease takes a dive down to a hospitalisation rate of 0.20 (20%) at a time when non-COVID respiratory admissions were being admitted at a rate of 0.60 (60%). Let us suppose that vaccines are doing their thing and keeping COVID cases out of hospital. So what’s with the curious red spike at week 20 (15 May – 21 May)? Do vaccines and viruses really play peek-a-boo like this or is something else going on?

Then we have to contend with the gradual increase in the COVID hospitalisation rate from week 23 onward - did the vaccines really stop working at a time when the second dose was being rolled out? With the (hypothesised) demise of vaccine efficacy COVID cases eventually manage to match the hospitalisation rate for non-COVID at 0.50 (50%) and we’re back at square one. No gain, no loss, just a truckload of money spent.