Natural seroconversion to high-risk human papillomaviruses (hrHPVs) is not protective against related HPV genotypes

The risk of seroconversion for multiple human papillomavirus (HPV) types over time was studied in a cohort of 532 women with cervical HPV infection, prospectively followed-up for > 10 y. Of the women who were HPV-antibody positive for at least 1 of the HPV types (6, 11 (low risk, lr), 16, 18, 31, 33, and 45 (high risk, hr)) at baseline, 73-98% seroconverted for 1 or more HPV types over time. Baseline lrHPV-seropositive women had 2.3-fold risk (95% confidence interval (CI) 1.1-4.7) for hrHPV seroconversion, but the opposite was not the case. Cross-protection by the natural HPV16 or HPV18 infection against other types of the HPV species A9 or A7 was not seen. These data suggest that protection against other HPV genotypes (as indicated by the lack of seroconversion) may not be provided by humoral HPV antibodies derived from a natural infection. Instead, these unvaccinated, HPV-antibody-positive women continue to be susceptible to infections by the other HPV genotypes over time.