This blog post is a very very good article from Blood Cancer UK and important reading for those moments when we need to be convinced of the reasons we are doing this very difficult thing.
Some more data has just been released which has looked at 17 MILLION people in the UK who are registered with a GP who uses a specific computer system. This is by far the largest study of its kind for COVID19 in the world.
It looks at the risk of dying in hospital from COVID19. I.e. it is asking how many people with different characteristics ended up dying in hospital from COVID19 and what factors are associated with being more likely to have that sad outcome.
The Hazard ratio for blood cancer was estimated and after adjusting for age and other factors that might also influence mortality from COVID19 these came out as 3.52 ( possible range 2.41-5.14) for those diagnosed in the last year, 3.12 (2.50-3.89) for those diagnosed between 1 and 5 years ago and 1.88 (1.55-2.29) for those diagnosed more than 5 years ago. These were among the highest individual risk factors of any condition.
A Hazard Ratio can be thought of as essentially indicating how much more likely an event is to happen. Thus for those who have been diagnosed with blood cancer within the last year the estimated risk they died from COVID was 3.5 times the normal population, and for one to five years the risk was 3 times the normal population and for those diagnosed longer ago it was approximately 2 times the risk of the normal population.
So here we are seeing that across the groups estimates the lowest possible range for the estimate for the risk would be 1.5 times the normal risk of dying from Covid and the highest possible estimate was 5 times the normal risk. That is quite a broad range of uncertainty and reflects that even a study of 17 million is not large enough nor has their yet been long enough time to give an absolute answer to this question. Everyone agrees that sadly before this epidemic is over a lot more people will die and so these estimates will become more accurate over time. But it would certainly seem to be the case the real risk must be significantly over 1 as the HR ranges do not come close to overlapping 1 (i.e. the lower range is not less than 1).
Mathematically you could in theory multiply those numbers by the risk for the general population of your own age and come up with an individual estimated risk.
Perhaps surprisingly there is a hint of a suggestion that the longer you have had blood cancer the less likely you are to die from COVID19 in hospital in the UK. Now remember this is not talking about the risk if you catch it but rather the risk dying from COVID19 being in the group described.
However we should note that these numbers will all be lower than they would otherwise be because of shielding. And since if you are shielding religiously it is essentially impossible to catch COVID19 if we all carry on shielding when this study is repeated in a few months these numbers may all come down further because people who are not shielding are obviously more likely to catch COVID19 in the first place.
So actually, and this is a hypothesis we cant be sure of, but if the trend towards a lower risk for those who have had blood cancer for longer is real (hard to say for sure when you look at the ranges around the estimates) then maybe that is because those patients were more likely to be already at least partially self isolating even before the letters came out.
Some of the people with blood cancer who have sadly died will have caught the disease before any lockdown or shielding instructions were issued. And so if people who have had blood cancer for longer are less likely to work, travel on public transport, and perhaps were quicker to respond to the advice from the government to shield then maybe that is why the estimate of the risk appears that their risk in practice was lower, but perhaps if nobody with blood cancer was shielding their risk might even have turned out to be higher than the newly diagnosed. We just don’t know.
Clearly we should be very careful to interpret too much into these findings. Except that it is another piece of evidence that strongly suggests that even though many of us have been shielding, there has up until now still been a significantly greater chance that people with blood cancer will die from COVID19 in the UK. But remember many of these people would have caught the disease before shielding or lock down started.
If every single patient with blood cancer decided in the light of this data to carefully sheild themselves then none of us would get COVID19 (except perhaps a few of us if we had to be admitted to hospital for some other reason and unfortunately caught it there) So when this study is repeated later on we might see these numbers drop lower and even ironically we might even then appear to be at lower risk than other people who don’t have blood cancer particularly once they start to lift lock down.
I think that society as a whole are doing us a great favour by giving us the advice and opportunity to shield and so avoid this risk. If you are shielding carefully you should not see any of this data as something to be anxious about since you are fully safe from COVID right now.
Here is the original paper: