Papanicolaou smears induce partial immunity against sexually transmitted viral infections.

Background: In a case-control study of hormonal contraceptives and invasive cervical cancer, an unexpected finding was a substantial decline in the prevalence of high-risk human papillomavirus (HPV) infection according to the lifetime number of Pap smears received. Here we assess the risk of 3 sexually transmitted viral infections -- herpes simplex virus 2 (HSV2), HPV, and human immunodeficiency virus (HIV) 1 and 2 -- in relation to the lifetime receipt of Pap smears.

Methods: Stored sera taken from 1540 controls were tested for HSV2 and HIV; cervical scrapings were tested for HPV.