I had a look and have a job figuring which bit you are looking at - I assume its from "Deaths occurring between 2 January and 2 July 2021 edition of this dataset"? Though that isn't really "March to August."
Have you considered that at the start of the year few people would have died 21 days after vaccination because that had only just happened. 6 months later more would have died as they would have had 6 months to get dying of various stuff.
Yes it starts in January but I mentioned March because it took some time for a large number of people to actually get the vaccine, and also there was probably flu going around in Jan/Feb. I should have said July not August.
The numbers reflect weekly, age standardised death rates. Therefore once you have a decent population size in each cohort, the timing shouldn’t matter. These are non-covid deaths so rates shouldn’t change except for normal seasonal patterns.
However it could be something like what JoshuaDavid mentions below - that healthy people are disproportionately being moved from the 21 days cohort to the second dose cohort by some selection mechanism.
If the vaccine was dangerous and resulting in “non covid” deaths, why would the mortality be lower for people who had a second dose than for people who just had 1 dose?
Commented separately but it’s pretty clear there’s some sort of selection effect going on with the people who are not getting a 2nd dose that makes them more likely to die of non-covid causes.
The 2nd dose cohort at that point had quite a different age profile (they were rolling out doses oldest to youngest). Over 50 age bands were 90%+ double dosed but 60% or less for under 50 age bands. It’s possible that older cohorts were out-performing typical mortality because of something like lack of flu due to lockdown.
Another possibility is that the first dose is an absorbing barrier if it causes so much illness and death that victims do not get a second dose. The two-dosed cohort are the “survivors” with the vulnerable already removed from the population.
And if the NHS and other experts noticed it, they for some didn’t include an explanation along with their other comments on the data.