The UK’s Covid-19 death toll has just passed 100,000 – for the second time.
It first passed 100,000 on January 7.
Now it has passed it again.
Why are there two death tolls – and why is one ahead of the other?
The answers lie in the way deaths are counted and reported.
Since the early weeks of the coronavirus pandemic in the UK, there have been two ways of measuring deaths.
One way is to count the number of people who have died within 28 days of testing positive for Covid-19.
This is the Government’s preferred measure, and this is the one that on Tuesday passed 100,000.
But there is another way to count deaths, based on the number of people who had Covid-19 recorded on their death certificate.
This is the one that passed 100,000 on January 7.
Using death certificates is the more comprehensive and reliable measure of the impact of Covid-19.
This is because it counts every single death that has involved coronavirus in the UK.
It is a more accurate indicator of what might have led to someone’s death, rather than a rule based simply on the number of days since a positive test.
By contrast, the Government’s method of only counting deaths with 28 days of a positive test is less comprehensive.
It does not include people who died more than 28 days after testing positive – even if those people spent that entire period in hospital and had Covid-19 marked on their death certificate.
It also excludes anyone who did not have a positive Covid-19 test.
Because of this, it undercounts the number of Covid-19 deaths that occurred during the first months of the pandemic, when only a minority of people were being tested.
For example, according to the figures for people who died within 28 days of a positive test, during the first wave of the virus the daily death toll peaked on April 8 at 1,073.
But according to death certificates, the number of Covid-19 deaths that occurred on April 8 was 1,457.
That is 36% higher.
This suggests hundreds of Covid-19 deaths that took place in the early weeks of the pandemic are not included in the figures based on the 28-day rule.
It is because of these reasons that the 28-day death toll is so much lower than the toll based on death certificates.
So why continue counting deaths using the 28-day rule?
There is one main reason: it is reported faster than the figures for death certificates.
It takes time for deaths to be registered and for the certificates to be filed – sometimes several weeks.
Deaths that are known to have happened within 28 days of a positive test can be reported to the UK’s health agencies and governments a lot quicker.
As such the 28-day figures are a useful early indicator of the overall trend in the number of deaths.
They are less useful for reflecting accurately the true impact of the coronavirus pandemic, however.
The cumulative death toll based on the 28-day rule currently stands at 100,162.
But the cumulative death toll based on death certificates currently stands at 108,084.
And when taking into account deaths that are known to have occurred since the publication of the latest statistics on death certificates, the overall toll is likely to be nearing 120,000.