Yes it was supposed to be 100% effective, then 95%, followed by 90%, now we see around 78% (as of September 2021). So it's effectiveness has either declined based on initial Pfizer/CDC claims compared to recent data, either that or they were exaggerating (or simply lying) about it's effectiveness from the start in order to get it "approved". As quite obviously 80% for vaccine effectiveness is still quite poor statistically speaking (compared to other vaccines) for multi-billion dollar funding and widespread use, unless it's a pandemic of course then more of a case of "throw against a wall and see if it sticks".
Pfizer/Moderna were claimed to be 90%+ effective against early variants, likely less so against Delta. Not sure about AZ (widely used in England).
Immunity does seem to decline over time (thus boosters). There is also data to suggest that vaccination followed by a COVID infection/recovery increases immunity compared to vaccination alone or infection alone.
Vaccination rate is not a static number. If we take UK population at 56.191M. According to the UK govt's data, in 2/2021 only 8,362,868 vaccinations had been administered (14.8% of the population). By 6/2021, only 33,085,145 had been administered (58.8% of the population). By end of 9/2021, they had administered 40,979,175 vaccines (72% of the population).
UK or England? Your charts referred to England. Did you exclude children under 18? You should because they weren't being vaccinated until later in the year. Even other age groups may need to be adjusted because the rollout started from the oldest.
So you do the math on what the "percentage vaxxed" was at the time the data was gathered.
If you do that you should adjust hospitalization/death data as well - it was not linear during that time period.
