Can STDs affect people at any age?

Yes. Age alone does not protect one from infections.
Yes. There are several that can pass from mother to her baby during pregnancy or delivery. They can also pass to an infant, child or pre-teen from sexual exploitation. They can also infect someone older .
YES. Any one who has had sexual contact, can be infected with an std. That includes babies and children who are sexually abused. Up to 2-3 percent of sexually abuse children will test positive for gonorrhea or chlamydia.