It does not matter if a man's penis has an infection or a man's vagina does, since both of them can infect the other and even ruin sex life for long. That is why both of you should pay attention to sexual health, especially because a vagina can catch a disease even without any infectious agents. Stress, poor hygiene, or even allergenic lotions and lubricants can lead to an imbalance in its flora, resulting in fungal and bacterial infections, which can spread to the penis, as well. Obviously, they can be prevented by proper personal hygiene, for instance. It does not mean that vaginal douche should be done every day – since it is also harmful for the vaginal flora – but rather that whatever is inserted in it should be clean. If it is a toy, it should be disinfected before the first usage at least, and if it is the penis, it should never be inserted back into the vagina after it has been pulled out of the rectum without proper disinfection.
But not only infections can affect vaginal health. It can also suffer from injuries called fissures that are caused by too harsh intercourse without proper lubrication. Friction of two dry surfaces will lead to burn scars, which can heal faster on the penis, since it is dry and open, but it may take as long as a month or even more for the vagina due to its wet, enclosed environment, and during this period, sex should be avoided. This is why prevention is easier than treatment, so use water-based neutral lubricants, or give enough time for the foreplay to avoid long, sexless periods.