It seems logical for two virgins to not be able to contract an STD after sex. After all, you can’t create an STD from nothing right?
That’s where you’re wrong: a person could still have an STD even though he or she has not had sex before. That’s because STDs are passed on in a variety of ways other than genital-to-genital contact. Therefore, the best way to keep your first time worry-free when it comes to STDs is to use a condom during sex.

Reference: https://asktheexperts.plannedparenthood.org/?p=5233/