Human Papillomavirus 16: Prevalence, Incidence, and Behavioral Risk Factors Deborah L. Thompson, MD, MSPH March 10, 2004

Background HPV is common viral STD > 30 HPV types infecting genital region Classified based on oncogenic potential Difficulties with HPV testing

Goals of study Characterize prevalence, persistence, and incidence of serologically determined HPV-16 Improve understanding of demographic and behavioral risk factors for seropositivity

Methods Study design –Cross-sectional for seroprevalence –Retrospective cohort for antibody persistence and seroincidence

Methods Population –Project RESPECT - STD Clinics –PR study participants were 5758 heterosexual pts aged 14 yrs or older –1595 patients used in current study

Study population

Methods Questionnaire data –Interviews at 0, 3, 6, 9, and 12 months Data for sera –Serum collected at 0, 6, and 12 months –IgG antibodies to HPV-16 by ELISA using virus-like particles

Outcome Definition Prevalent infection: seropositive at baseline Persistent infection: seropositive at baseline and at 6 and 12 months Incident infection: seronegative at baseline with subsequent seropositive result at 6 and/or 12 months

Statistical analysis Point prevalence and incidence density Simple logistic regression Multiple logistic regression

Study Population (n=1595) Female50.7% White28.5% Black48.6% Hispanic13.4% Age <20 yrs15.9% Age yrs28.3% Age yrs31.2% Age >35 yrs24.6%

Study Population (n=1595) Median # lifetime partners (interquartile range) 18.0 (8-40) Mean # partners past 3 months (+ SD)

Results: HPV-16 Seroprevalence Overall, 24.5% (95% CI 22.4, 26.6) Higher among women (30.2%) than men (18.7%, OR 2.1, 95% CI 1.6, 2.8)

Results: HPV-16 Seroprevalence *Adjusted for race/ethnicity, education, income, and study site. VariableAdjusted OR (95% CI)* Female2.1 (1.6, 2.8) Age yrs1.9 (1.2, 2.9) Age yrs2.4 (1.6, 3.7) Age >35 yrs2.0 (1.3, 3.1) 3-10 episodes sex with occasional sex partner 1.7 (1.3, 2.4)

Results: HPV-16 Seroincidence Overall incidence 20.2 cases per 100 person-years (95% CI 17.9, 22.5) Women: 25.4 cases per 100 person-years (95% CI 21.8, 29.0) Men: 15.7 cases per 100 person-years (95% CI 12.9, 18.5)

Results: HPV-16 Seroincidence *Adjusted for race/ethnicity, arm, study site, and income. VariableAdjusted OR (95% CI)* Female1.8 (1.3, 2.5) Age yrs1.8 (1.0, 3.1) Age yrs2.0 (1.1, 3.5) Age >35 yrs2.1 (1.2, 3.6) Baseline ELISA > than median1.6 (1.2, 2.3) 1-2 times unprotected sex with occasional partner 1.7 (1.2, 2.4)

Study limitations No gold standard Potential for misclassification Limited generalizability

Conclusions Seroprevalence and seroincidence higher among women than men Age > 20 years independently associated with seroprevalence and seroincidence Recent sexual behavior was stronger predictor than lifetime sexual behavior