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Original Investigation
April 2015

Incidence of Sexually Transmitted Infections After Human Papillomavirus Vaccination Among Adolescent Females

Author Affiliations
  • 1Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts
  • 2Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts
  • 3National Bureau of Economic Research, Cambridge, Massachusetts
  • 4Leonard D. Schaeffer Center for Health Policy and Economics, University of Southern California, Los Angeles
  • 5Department of Emergency Medicine, University of Southern California, Los Angeles
JAMA Intern Med. 2015;175(4):617-623. doi:10.1001/jamainternmed.2014.7886

Importance  Human papillomavirus (HPV) vaccination rates among US females remain low, in part because of concerns that HPV vaccination may promote unsafe sexual activity by lowering perceived risks of acquiring a sexually transmitted infection (STI).

Objective  To study whether HPV vaccination of females is associated with increases in STI rates.

Design, Setting, and Participants  Using a large, longitudinal insurance database of females aged 12 to 18 years insured from January 1, 2005, through December 31, 2010, in the United States, we examined whether HPV vaccination was associated with an increase in incident STIs among females who were vaccinated compared with those who were not. We defined STIs as one or more medical claims for any of the following infections in a given quarter: chlamydia, gonorrhea, herpes, human immunodeficiency virus or AIDS, or syphilis. We used difference-in-difference analysis to compare changes in STI rates among HPV-vaccinated females before and after vaccination (index quarter) to changes among age-matched nonvaccinated females before and after the index quarter. We analyzed whether effects varied according to age and prior contraceptive medication use.

Main Outcomes and Measures  Rates of STIs.

Results  The rates of STIs in the year before vaccination were higher among HPV-vaccinated females (94 of 21 610, 4.3 per 1000) compared with age-matched nonvaccinated females (522 of 186 501, 2.8 per 1000) (adjusted odds ratio, 1.37; 95% CI, 1.09-1.71; P = .007). The rates of STIs increased for the vaccinated (147 of 21 610, 6.8 per 1000) and nonvaccinated (781 of 186 501, 4.2 per 1000) groups in the year after vaccination (adjusted odds ratio, 1.50; 95% CI, 1.25-1.79; P < .001). The difference-in-difference odds ratio was 1.05 (95% CI, 0.80-1.38; P = .74), implying that HPV vaccination was not associated with an increase in STIs relative to growth among nonvaccinated females. Similar associations held among subgroups aged 12 through 14 years and aged 15 through 18 years and among females with contraceptive use in the index quarter.

Conclusions and Relevance  Human papillomavirus vaccination was not associated with increases in STIs in a large cohort of females, suggesting that vaccination is unlikely to promote unsafe sexual activity.