Put a number on 'very effective'.
Previous infection alone can confer 90% protection against severe disease according to a study in The Lancet.
But, people are assigning that protection to the vaccine in many cases.
"We identified a total of 65 studies from 19 different countries. Our meta-analyses showed that protection from past infection and any symptomatic disease was high for ancestral, alpha, beta, and delta variants, but was substantially lower for the omicron BA.1 variant.
Protection against severe disease remained high for all variants, with 90·2% (69·7–97·5) for ancestral, alpha, and delta variants, and 88·9% (84·7–90·9) for omicron BA.1 at 40 weeks."