Donken et al,8 2018 | Netherlands | Longitudinal follow-up study using online questionnaires | Age 16–17 y at inclusion; 1938 vaccinated and 1051 unvaccinated | Vaccinated participants were more likely to have ever had sex (OR = 1.19, 95% CI 1.02 to 1.39) and this difference increased over time (OR = 1.06, 95% CI 1.00 to 1.12); however, after correction for sociodemographic factors, no difference was observed | Unvaccinated participants had a slightly higher lifetime number of partners (mean difference of −0.20, 95% CI −0.41 to 0.00) | No difference was observed for condom use with a casual partner. Vaccinated participants were less likely to always use a condom with their steady partner (adjusted OR = 0.71, 95% CI 0.57 to 0.89) |
Liddon et al,10 2012 | United States | Data from the National Survey of Family Growth | Age 15–24 y; 279 vaccinated and 964 unvaccinated | Having had vaginal sex was unrelated to receipt of HPV vaccine | NA | Vaccinated females were more likely to use condoms consistently in the past 4 weeks (OR for always wearing a condom was 3.0, 95% CI 1.1 to 7.9) |
Kumakech et al,12 2017 | Uganda | Population-based comparative cross-sectional survey | Age 15–24 y (median age was 18.6 y); 438 females (53% of whom were vaccinated) | NA | No significant differences between vaccinated and unvaccinated participants in number of sexual partners in the previous 3 mo, the previous 1 y, the previous 4 y, or their lifetime | No significant difference in having ever used a condom between vaccinated and unvaccinated participants |
Cummings et al,14 2012 | United States | Comparison of a group of vaccinated adolescent girls with historical controls. Questionnaires and clinician or self- collected vaginal swabs | Age 14–17 y; 75 vaccinated and 150 matched unvaccinated | No difference in being sexually active at enrolment between unvaccinated (76.2%) and vaccinated participants (73.6%), P = .65. | No significant difference in number of sex partners in the past year (OR = 1.1, 95% CI 0.9 to 1.3) or in the past 2 mo (OR = 1.2, 95% CI 0.9 to 1.5) | Mean instances of vaginal intercourse without a condom in the past 2 mo were significantly lower among vaccinated adolescent girls (OR = 0.5, 95% CI 0.4 to 0.6) |
Sadler et al,15 2015 | United Kingdom | Clinical histories from genitourinary medicine clinic visitors | Age 14–20 y; 231 vaccinated and 132 unvaccinated | NA | No difference was observed in the proportion of participants with >6 lifetime partners between vaccinated and unvaccinated females. Vaccinated females were more likely to have had ≥3 partners in the past 6 mo (OR = 2.12, 95% CI 1.08 to 4.17) | Condom use at first intercourse contact was slightly higher among vaccinated females (OR 0.55, 95% CI 0.32 to 0.96), while condom use at last intercourse contact was not significantly different |
Forster et al,16 2012 | United Kingdom | Cross-sectional and longitudinal surveys | Age 16–17 y; 433 vaccinated and 620 unvaccinated | No difference between the group being offered the HPV vaccine and the group who had not been offered the vaccine (OR 0.98, 95% CI 0.70 to 1.38). Also, no difference in the group becoming sexually active over time (OR 0.80, 95% CI 0.40 to 1.59) | No significant difference in the change in number of sexual partners over time between the 2 groups | No significant difference in change in inconsistent condom use between the 2 groups (OR 0.88, 95% CI 0.58 to 1.33) |