I get my booster shot every year, the same for flu shot.

If every Brit had access to the vaccine at the same time, that chart may say something, but perhaps the NHS roll out timeline matters too...

Availability of vaccine appointments in England, by date
Start date Appointments available for Priority
group

Ref
8 December 2020 Residents in a care home for older adults and their carers; and all aged 80 and over 1 and part of 2 [44][45]
Procedures set out on 9 and 14 January 2021 Frontline health and social care workers Part of 2 [46][47]
18 January 2021 All aged 70 and over, and clinically extremely vulnerable individuals 3 and 4 [48]
15 February 2021 All aged 65 and over; and those aged 16 to 64 with underlying health conditions which put them at higher risk of serious disease and mortality 5 and 6 [49]
1 March 2021 All aged 60 and over 7 [50]
6 March 2021 All aged 56 and over 8 (age adjusted from 55) [51]
17 March 2021 All aged 50 and over 9 [52]
13 April 2021 All aged 45 and over [53]
26 April 2021 All aged 44 and over [54]
27 April 2021 All aged 42 and over [55]
30 April 2021 All aged 40 and over [56]
13 May 2021 All aged 38 and over [57]
18 May 2021 All aged 36 and over [58]
20 May 2021 All aged 34 and over [59]
22 May 2021 All aged 32 and over [60]
26 May 2021 All aged 30 and over [61]
8 June 2021 All aged 25 and over [62]
15 June 2021 All aged 23 and over [63]
16 June 2021 All aged 21 and over [64]
18 June 2021 All adults (ie aged 18 and over)