According to this, it
might be best to get the booster in the same arm as the prior jabs:
>>>The immune response may be stronger if your booster goes in the same arm as your last Covid-19 shot, according to a
study published August 11 in the journal eBioMedicine. . . . Two weeks after the booster, the number of “killer T cells” was significantly higher in those who had both shots in the same arm, according to the study. Those cells, which attack and destroy the other cells they target, were present in 67% of the same-arm cases and only 43% in people who had their injections in different arms, according to study coauthor Laura Ziegler, a doctoral student at Saarland University. . . . Although the study showed a greater immune response, researchers can’t say for sure that getting the booster in the same arm results in better or longer lasting protection, Schaffner said. “We wouldn’t know that unless we did a much larger clinical study with follow-up actual infections,” he added.<<<
I've always thought that "killer T cells" are the badasses of the immune system. Hopefully the "wimpy little cells that don't really do jack" aren't too upset about it.