Estimating effectiveness of HPV vaccination against HPV infection from post-vaccination data in the absence of baseline data

Prevalence of human papillomavirus (HPV) types 16 and 18 in cervical cancer in Stockholm, Sweden during 2019-2023 compared to 2003-2008

BACKGROUND

The prevalence of different HPV types, especially HPV16 and 18 in cervical cancer in patients diagnosed 2019-2023 in Stockholm was compared to corresponding data from 2003-2008 before the introduction of HPV vaccination in Sweden.

MATERIAL AND METHODS

Cervical cancer samples from 125 patients diagnosed 2019-2023 in Stockholm were analysed for 27 HPV types by multiplex assay and the HPV type prevalence data was compared to data obtained in 154 cervical samples from 2003-2008.

RESULTS

Patient median age was higher 2019-2023 compared to 2003-2008 (55-years vs. 42-years, p = 0.046). Overall HPV prevalence was 93.6%, HPV16 and 18 accounted for 62.2% of all squamous cell carcinoma cases (SCC) and 63.6% of all adenocarcinoma cases (ADC) vs. 92.9%, 69.7% and 88.6% respectively 2003-2008.

CONCLUSION

The joint prevalence of HPV16 and 18 in SCC and ADC tended to be slightly lower in 2019-2023 as compared to 2003-2008, but the difference was not statistically significant.

Real-world impact and effectiveness assessment of the quadrivalent HPV vaccine: a systematic review of study designs and data sources

INTRODUCTION

Vaccine effectiveness and impact studies are typically observational, generating evidence after vaccine launch in a real-world setting. For human papillomavirus (HPV) vaccination studies, the variety of data sources and methods used is pronounced. Careful selection of study design, data capture and analytical methods can mitigate potential bias in such studies.

AREAS COVERED

We systematically reviewed the different study designs, methods, and data sources in published evidence (1/2007-3/2020), which assessed the quadrivalent HPV vaccine effectiveness and impact on cervical/cervicovaginal, anal, and oral HPV infections, anogenital warts, lesions in anus, cervix, oropharynx, penis, vagina or vulva, and recurrent respiratory papillomatosis.

EXPERT OPINION

The rapid growth in access to real-world data allows global monitoring of effects of different public health interventions, including HPV vaccination programs. But the use of data which are not collected or organized to support research also underscore a need to develop robust methodology that provides insight of vaccine effects and consequences of different health policy decisions. To achieve the WHO elimination goal, we foresee a growing need to evaluate HPV vaccination programs globally. A critical appraisal summary of methodology used will provide timely guidance to researchers who want to initiate research activities in various settings.

Human papilloma virus (HPV) prevalence upon HPV vaccination in Swedish youth: a review based on our findings 2008-2018, and perspectives on cancer prevention

PURPOSE

Three human papillomavirus (HPV) vaccines are available against up to nine HPV types. In Sweden, from 2012, Gardasil was offered to 10-12 year old girls through the school-based vaccination program, and as catchup vaccination for women up to 26 years. To obtain a baseline, and follow HPV vaccination effects, during 2008-2018, cervical and oral HPV prevalence were followed at a youth clinic in Stockholm, and in 2013 for comparison oral HPV prevalence was examined in high-school youth in a middle-sized county in Sweden.

METHODS

In this review, we discuss all our data with cervical and oral mouthwash samples that were collected and tested for 24-27 HPV types by a bead-based multiplex assay from 2008.

RESULTS

Compared with 2008-2011, with ~ 35% HPV16 and > 60% high risk (HR) HPV cervical prevalence at the youth clinic, a decrease of vaccine HPV types was observed between 2013 and 2018, with e.g., HPV16 falling to 5% in catchup vaccinated women and 15-18% in nonvaccinated women. Most common cervical HR-HPV types were HPV39, 51, 52, 56, and 59 together accounting for ~ 10% of cervical cancer, and where only HPV52 is included in Gardasil-9. At baseline 2009-2011, oral HPV prevalence was ~ 10% in unvaccinated youth at the youth clinic, but after 2013 it dropped to < 2% at the youth clinic and high schools.

CONCLUSION

To conclude, Gardasil HPV types have decreased, but it is still important to follow remaining HR-HPV types and cancer development, since there is an ongoing increase in the incidence of HPV-associated tonsillar and base of tongue cancer, and cervical cancer in Sweden.

Changes in Cervical Human Papillomavirus (HPV) Prevalence at a Youth Clinic in Stockholm, Sweden, a Decade After the Introduction of the HPV Vaccine

Aim: This study aimed to follow the impact of human papillomavirus (HPV) catch-up and vaccination on the very high cervical HPV-prevalence in women at a youth clinic in central Stockholm during the period 2008–2018.

Background: 2008–2010, cervical HPV-prevalence (69.5%) and HPV16 prevalence (34.7%) were high in non-vaccinated women at a youth clinic in Stockholm. 2013–2015, after the introduction of the quadrivalent-Gardasil® HPV-vaccine, HPV16 and HPV6 prevalence had decreased. Here, cervical HPV-prevalence was investigated 10 years after primary sampling.

Material and Methods: 2017–2018, 178 cervical swabs, from women aged 15–23 years old, were tested for 27 HPV types by a bead-based multiplex method. HPV-prevalence data were then related to vaccination status and age and compared to HPV-prevalence in 615 samples from 2008 to 2010 and 338 samples from 2013 to 2015 from the same clinic, and to HPV types in 143 cervical cancer cases during 2003–2008 in Stockholm.

Results: The proportion of vaccinated women increased from 10.7% (2008–2010) to 82.1% (2017–2018). The prevalence of all 27 HPVs, all high-risk HPVs (HR-HPVs) and the combined presence of the quadrivalent-Gardasil® types HPV16, 18, 6, and 11, was lower in vaccinated compared to unvaccinated women (67.4 vs. 93.3%, p = 0.0031, 60.1 vs. 86.7%, p = 0.0057 and 5.8 vs. 26.7%, p = 0.002, respectively). Furthermore, HPV16 prevalence in non-vaccinated women 2017–2018 was lower than that in 2008–2010 (16.7 and 34.7%, respectively, p = 0.0471) and similar trends were observed for HPV18 and 11. In both vaccinated and non-vaccinated women, the most common non-quadrivalent-Gardasil® vaccine HR-HPV types were HPV39, 51, 52, 56, and 59. Together they accounted for around 9.8% of cervical cancer cases in Stockholm during 2003–2008, and their prevalence tended to have increased during 2017–2018 compared to 2008–2010.

Conclusion: Quadrivalent-Gardasil® vaccination has decreased HPV-vaccine type prevalence significantly. However, non-vaccine HR-HPV types remain high in potentially high-risk women at a youth clinic in Stockholm.