You should not have intercourse on the second day of vaginal pills because during the pills, the vaginal environment is slowly recovering due to the effects of the pills. If you have intercourse too early at this time, it will aggravate the vaginal infection and a large amount of medication will remain in the vagina, which will cause cross-transmission of diseases and will make it easier for the vaginal infection to persist. If you want to have intercourse, you should do it as much as possible the day after the pill is inserted, that is, two days after the pill is not inserted. This is to give the medication a chance to be absorbed and to avoid affecting the effectiveness of the treatment.