After our second shot we were both lethargic for a day but that means it is working. My wife had a booster shot and zero issues after
I’m coming off of covid so have to wait 3 months for the booster.
My 1st shot was a non-event sans normal sore shoulder.
2nd shot was as I described, feeling tired and lethargic next day. My biologist daughter told me the same thing as you said, that it means it was working. Booster was same as 2nd shot.
Since my 1st shot in February 2021, I have done 3 cruises, 2 more booked in January and February 2022, countless visits to grocery stores, restaurants, cancer clinic to escort my wife, and other normal activities of living a life, and not any symptoms of covid. Nothing, nada, zero, shunya.