Dear Doctor, We Had 2 First Dozes Of Painfull Vaccine

Dear Doctor, we had 2 first dozes of painfull vaccine against difteria et cetera. My child got severe seizures for 4 days followed by other side effects, due to which doctor advised to go for Pentaxim and we successfully had it later. Now we have our 18 months booster shot and vaccine is not available. I would like to give it back in Europe where it is being given and has no issues, however we would be having around 8 months gap from last shot. would it be fine since it is a booster?

thank you in advance