This is probably the most underrated comment. Very few people think twice about e.g. driving a car, but a lot of people are scared of flying. It can also be as simple as being afraid of needles; when I get vaccinated I barely feel it but even knowing that I'm still apprehensive beforehand.

Hopefully, as more people get vaccinated, it will become somewhat normalised (in communities that aren't actively against it). If all your mates did it, it's probably fine. (no sarcasm)