Looking at economics just evaluating your immunity (doctor, test, doctor) is probably far more expensive and inconvenient than just getting vaccinated using mass vaccination facilities.
In France a non specialist doctor visit is 25 EUR, analysis of simplest kind is about 100 EUR, then you need another visit then may be another action (medication, more analysis).
Mass vaccine is about 20 EUR a shot.
In 2021 so far testing for COVID costed more than vaccine in France (6.2 vs 5.8 billions EUR).
In France a non specialist doctor visit is 25 EUR, analysis of simplest kind is about 100 EUR, then you need another visit then may be another action (medication, more analysis).
Mass vaccine is about 20 EUR a shot.
In 2021 so far testing for COVID costed more than vaccine in France (6.2 vs 5.8 billions EUR).