I got the J&J back in early April which was all I could get my hands on back then(no side effects aside from a sore arm). After seeing its efficacy (specially against the delta variant) I went and got a Pfizer shot in early July which hit me like a truck. Since I was already "fully vaccinated" I delayed the second dose of my Pfizer shot till now (~10 weeks) to maximize the induced immunity. I gotta say the second dose of Pfizer only give me mild side effects for half a day.