Honest query: Since I didn't see this asked in other answer threads, are only children at risk or adults can contract it too? How likely is it to spread from in

Honest query: Since I didn't see this asked in other answer threads, are only children at risk or adults can contract it too? How likely is it to spread from indected individual. The vaccination is done in childhood. I received three doses before 8 y.o., but I am not certain if this is relevant to adults & getting infected in e.g 30s. Thx in advance