How long after taking doxycycline can cervicitis symptoms persist?

Cervicitis. The causes of cervicitis are not well understood. Some cases are due to chlamydia, gonorrhea, or other STDs. Antibiotics, including doxycycline, often are tried, but often they make no difference. If symptoms continue (e.g. vaginal discharge, spotting after sex, etc), recheck with your doctor.
Varies. The symptoms may not be entirely due to the active infection but can also come from the damage incurred during the infection. A test of cure is important if the symptoms persist.