The Pfizer and Moderna vaccines were authorized for use by the FDA in mid December 2020. Per California's regs - states controlled distribution in-state, not the Feds - I was too young at the time to receive a vaccination. California lifted the age restriction in, IIRC, March 2021. I got Covid in January 2021, when I was still too young to be vaccinated. When I was released from the hospital my doctor advised me to wait 90 days before being vaccinated. Consequently, I was finally vaccinated in spring 2021.
Then, some 6 months later, because the Feds were suggesting that vaccination was only good for six months, I did the test for Covid antibodies. The test I did did not discern between antibodies from recovery vs. vaccination. My antibody level was greater than the measurement range of the test. Recently I learned that those who have recovered and have been vaccinated have better immune response than those who have had one or the other, but not both.
Despite at least two known exposures, one being in a car for an hour with a person who had Covid instead of the cold they thought they had (summer 2024), I've not gotten Covid, that I know of, since January 2021. Figuring that ~3 1/2 years was a reasonable wait and mutations had accumulated, I got a booster in fall 2024. I'm in no way fearful or immune-compromised, as some DU-folk seem to be, but it's not like the Covid vaccine boosters are a first among vaccinations.
Covid had become less deadly, per case, in winter 2021-2022 than it had been in winter 2020-2021. Discerning how much of that was due, severally, to recovery immunity, vaccine immunity, and mutation, I've not seen estimated. Personally, I think it's all of the above, in significant degrees from each. My opinion and a tenner will get you a latte' and change at Peet's coffee.