That depends on individuals reactions. I had Pfizer
- no reaction to the first shot not even a sore arm,
- an adverse reaction to the second shot - approximately 14 hours of chills (wearing two sets of thermals, full ski gear, two doonas and sitting in front of a heater when it was 25 degrees outside)
- Had booster three and a half weeks ago and still struggling - chills, sweats, headaches, nausea and a sore arm for the first two weeks including a bruise and lump in the armpit of the injected arm. Still experiencing mild nausea and headaches from time to time but generally now it is just ongoing fatigue.
I have no health issues other than an underactive thyroid controlled by medication so guess I am just one of the unlucky ones. Probably biggest issue was that I could not stop for a day off as I clear the border and we are seriously short staffed - my own worst enemy. That said, I would still have the booster/s when they come up - if I feel that coughpy from the vaccine then chances are I would not make it through if I actually caught Covid.
Only query I would have with having booster shots early would be if travel insurance was still valid? Yes you would be vaccinated but you would not have had the shots at the required intervals if you have them early. Not sure how early shots work with the efficacy of the vaccine.
Medicare updated my vaccination status the following day so proof was quick.
Enjoy your travels - lucky you!