Licensed human papillomavirus (HPV) vaccines are expected to prevent high-risk (hr) HPV-infections (most notably types 16 and 18). Whether HPV vaccination will change the distribution of hrHPVs at the population level is open, since competition between HPV types is not well understood. Two stratified random subcohorts (1983-1997 and 1995-2003) of 7,815 and 3,252 women with a minimum of 2 pregnancies (<32 years) were selected from the Finnish Maternity Cohort. Using ELISA based on virus-like particles (VLP), we determined antibodies to HPV11, 16, 18 and 31 in paired sera of the women and used Poisson regression models to estimate the risk of further infection with other HPV types in those positive for HPV16 or HPV18 at baseline. Baseline HPV16 seropositivity was associated with increased risk of later infections with HPV18 (3.1, 95% CI: 1.7, 5.6). HPV18 seropositivity was associated with increased risk of HPV16 (3.9, 95% CI: 2.5, 6.1). Our observations favor a coinfection rather than superinfection model for the different HPV types and are not suggestive for type-replacement following HPV vaccination.
(c) 2009 UICC.