Sure and we can all have our views on what is happening with the coronavirus and even more so with what should be. Just to be open about it mine is it’s endemic now so open up again and suck it up.
But such views – perhaps more correctly described as different evaluations of the trade offs – do not excuse people simply getting the underlying logic wrong. As in this in The Guardian:
Why has the mortality rate for coronavirus decreased in the UK? The Intensive Care National Audit and Research Centre has analysed data from more than 10,000 patients admitted to intensive care units in England, Wales and Northern Ireland, and shown that the 28-day mortality of patients admitted to ICU has fallen from 43.5% before the April peak to 34.5% after the peak – a decrease of nine percentage points.
That’s not actually the Covid-19 mortality rate. Rather, that’s the rate of those sent into ICU from Covid-19. That’s sorta trivial but the logical error isn’t.
Some have suggested this may be due to “herd immunity” or that over time we have learned how to successfully treat this disease. But there’s scant evidence to support these claims. So what’s going on?
It’s not going to be anything to do with herd immunity because that would mean people don’t catch it and aren’t sent into ICU to die or not from it. That is herd immunity changes – if it exists of course – the numbers before we’ve started counting by this measure.
Emerging data suggests that some people who have not been exposed to Sars-Cov-2 have a type of white blood cell (T cell) that recognises the virus because it has previously been exposed to other coronaviruses, such as the common cold. Whether these cross-reactive T cells prevent or lessen the impact of infection in people with coronavirus is not yet known. It’s an intriguing preliminary finding, but there’s currently no evidence that we have herd immunity in the UK.
Studies have consistently shown that fewer than 20% of the UK population have antibodies to coronavirus in their blood, and we don’t fully understand the mechanisms by which our immune systems deal with this new virus effectively.
The term herd immunity is ill-defined and unhelpful. It suggests that we can now relax our adherence to measures such as social distancing and facial coverings.
All of which is entirely irrelevant. The measure used at the top is about how many die once caught. All the discussion is about how many catch.
Think back to the last pandemic for a moment. We can treat – although very rarely cure – HIV these days. But the limitation of the disease was rather about don’t share needles and be a bit more careful about sharing gonads. Further, we don’t measure the success of failure of Retrovir by the change in behaviour in bathhouses. They are different things, to be measured differently, and the success or failure of one does not change the success or failure of the other.
Fewer people dying in ICU tells us about treatment in ICU. It does not tell us about herd immunity nor T-cells stopping the initial infection and all that.
Dr Charlotte Summers is a lecturer in intensive care medicine at the University of Cambridge
Trust The Guardian to hire the wrong person to write the piece.