Follow-up on oral and cervical human papillomavirus prevalence 2013–2015 in youth at a youth clinic in Stockholm, Sweden

In 2009–2011, among young people aged 15–23 years who were not vaccinated against human papillomavirus (HPV), the prevalence of cervical HPV was 70%, with 34.7% being HPV 16-positive at a Stockholm youth clinic, while the prevalence of oral HPV was 9.3% [1,2]. In addition, high frequencies of highrisk (HR-HPV) 51 (10.7%), 18 (10.1%) and 52 (9.9%) were observed in cervical samples [1]. In a follow-up study performed from October 2013 to April 2014 at the same youth clinic, we recently reported that 73% of the women had been vaccinated against HPV (the majority with Gardasil), but not necessarily before sexual debut [3]. At this time, overall oral HPV prevalence and cervical HPV 16 prevalence had decreased significantly [3]. Oral HPV prevalence was now 1.4% and cervical HPV 16 prevalence was significantly lower, with 5% in vaccinated as compared with 24% in non-vaccinated individuals [3]. Moreover, there was also a significant decrease in cervical prevalence of HPV 31 and 70 between vaccinated and non-vaccinated individuals [3]. The previous follow-up study has now been extended from May 2014 to May 2015 and here we present an updated report from October 2013 to May 2015, including 457 mouthwash samples (335 from women and 122 from men) and 338 cervical samples. The study was performed according to ethical permissions from the Stockholm Regional Ethical Committee. Vaccination against HPV was self-reported. No behavioural data were acquired. Oral samples, collected in 50% Listerine as described previously or Scope mouthwash, were spun down and stored at –20 C [1,2]. Cervical samples were collected in SurePath solution and stored at +4 C [1,2]. Following DNA extraction and multiplex PCR, the presence of 27 HPV types was evaluated by a bead-based Luminex assay as reported; however, since then the evaluation of the HPV 33 E6 region has also been included [3,4]. During the whole follow-up period from October 2013 to May 2015, 71% of the women reported being catch-up vaccinated. Oral HPV prevalence was 1.5%, with 7/457 samples being positive for HPV DNA, of which 3 were from men and 4 from women, with only one being positive for HPV 16. Cervical HPV prevalence was 64.6% in vaccinated and 74.5% in nonvaccinated women (p1⁄4 0.096), with a lower HR-HPV type frequency in vaccinated as compared with non-vaccinated women (50.8% and 62.2%, respectively, p1⁄4 0.031). Moreover, HPV 16, HPV 31 and HPV 6, were significantly lower in frequency in cervical samples from vaccinated as compared with non-vaccinated women (p1⁄4 0.0006, p1⁄4 0.038 and p1⁄4 0.009, respectively) (Figure 1). In addition, there was a significant decrease in cervical HPV 16 prevalence in nonvaccinated women in 2013–2015 (18%), as compared with nonvaccinated women in 2008–2011 (34.7%) [1], p1⁄4 0.00038. Currently, the five most common HR-HPV types are HPV 59, 56, 51, 52 and 39. For details of cervical HPV prevalence in vaccinated and non-vaccinated women during 2013–2015 in comparison with non-vaccinated women during 2008–2011 see Figure 1. To conclude, in this extended follow-up study, catch-up vaccination frequency was 71%, and both oral HPV prevalence at 1.5% for the whole cohort, and cervical HPV 16 prevalence at 5% in vaccinated women remained low. There was a significant decrease in cervical HPV prevalence of both the vaccine types 16 and 6, as well as the non-vaccine type 31 (but not for HPV 70 in this study as compared with that reported before) in vaccinated as compared with non-vaccinated women.