In the first eight weeks of the Spring 2025 booster campaign just under 3.6 million doses have been administered in England. 

Number of doses per week by vaccination campaign in England: Week ending Mar 7, 2022 - May 25, 2025

Eligibility for the Spring Booster campaigns is the same for each year so are comparable, whereas the Autumn 2022 campaign was offered to a larger cohort than the following Autumn campaigns so should not be compared to these years.
Chart: Bob Hawkins Source: NHSE Get the data Created with Datawrapper