9 (1.4–2.6)) and chlamydia infection (30% vs. 15% prevalence in those with and without chlamydia, adjusted OR 1.8 (1.2–2.7) in NCSP participants (Supplementary Table 2). The most common HPV type in each group was HPV 16 (Table 3). HPV 51 and 18 were the next most commonly detected types overall. Although the order varied slightly, there was some consistency between the groups in terms of the six most commonly detected HR types (HPV 16, 18, 39, 51, 52 and 59, with the exceptions of HPV 56 replacing HPV 52 for group 2 and HPV 31 replacing HPV 39 in group 3, Table 3). The

prevalence of types closely related to vaccine HPV types and types against which cross-protection have been reported in clinical trials are shown in Table 3. HPV types 31, 33, 45, 52 or 58 were detected in 16% of NCSP 16–24 year olds (group 1), while the subset of HPV types 31, 33 and 45 against which stronger cross-protection has been reported were detected NVP-BGJ398 in 8.8% (Table 3) [2]. HPV types 6 and/or 11 were detected in 5.8%, 4.9% and 2.4% of groups

1, 2 and 3 respectively. In each group, HPV 6 was the more common infection and overall was present in 85% of HPV 6/11 infections. In our samples of young women undergoing chlamydia screening, prior to mass HPV immunisation, HR HPV (particularly types 16, 18 and 51) and multiple HPV infections were common. The prevalence of HR HPV, HPV 16/18 and multiple HPV infections showed similar patterns consistent with epidemiology 3-deazaneplanocin A price determined by sexual activity (of women and of their partners), with strongest and most consistent associations found for increasing age (up to 19 years), multiple sexual partners and presence of chlamydia infection. Our baseline,

pre-immunisation estimates of vaccine-type infection (HPV 16/18) prevalence in 16–24 year olds undergoing routine chlamydia screening not through the NCSP sites included in this study was 18% (95% CI 16–19). Any of the group of five related HR HPV types for which vaccine trials have reported cross protection (HPV 31, 33, 45, 52, 58) were found in 16% (95% CI 14–18) of this sample of young women. This multi-centred, community-based study was not population-based but instead made use of convenience sources of residual samples from young women undergoing chlamydia testing. In 2008/09, 15% of females aged 15–24 years were tested for chlamydia through the NCSP [20]. Our sample of NSCP participants was representative of all participants in 2008/09 at our selected venues. The women included in our survey were sexually active, and had higher risk behaviour than the general population. NSCP participants more commonly report multiple sexual partners and non-condom use at last sexual intercourse than the general population [21] and chlamydia positivity amongst NSCP screens is also higher than estimates of population prevalence [20] and [22].