Cervical Cancer Incidence in Young U.S. Females After Human Papillomavirus Vaccine Introduction

Introduction

Since 2006, human papillomavirus vaccine has been recommended for young females in the U.S. This study aimed to compare cervical cancer incidence among young women before and after the human papillomavirus vaccine was introduced.

Methods

This cross-sectional study used data from the National Program for Cancer Registries and Surveillance, Epidemiology, and End Results Incidence–U.S. Cancer Statistics 2001–2014 database for U.S. females aged 15–34 years. This study compared the 4-year average annual incidence of invasive cervical cancer in the 4 years before human papillomavirus vaccine was introduced (2003–2006) and the 4 most recent years in the vaccine era (2011–2014). Joinpoint regression models of cervical incidence from 2001 to 2014 were fitted to identify the discrete joints (year) that represent statistically significant changes in the direction of the trend after the introduction of human papillomavirus vaccination in 2006. Data were collected in 2001–2014, released, and analyzed in 2017.

Results

The 4-year average annual incidence rates for cervical cancer in 2011–2014 were 29% lower than that in 2003–2006 (6.0 vs 8.4 per 1,000,000 people, rate ratio=0.71, 95% CI=0.64, 0.80) among females aged 15–24 years, and 13.0% lower among females aged 25–34 years. Joinpoint analyses of cervical cancer incidence among females aged 15–24 years revealed a significant joint at 2009 for both squamous cell carcinoma and non–squamous cell carcinoma. Among females aged 25–34 years, there was no significant decrease in cervical cancer incidence after 2006.

Conclusions

A significant decrease in the incidence of cervical cancer among young females after the introduction of human papillomavirus vaccine may indicate early effects of human papillomavirus vaccination.

Introduction

Cervical cancers are caused by human papillomavirus (HPV) infections.¹ HPV vaccination was introduced in the U.S. in 2006. Currently, there are three types of HPV vaccines available: bivalent,² quadrivalent,³ and nonavalent.⁴ The bivalent and quadrivalent vaccines protect against HPV 16 and 18, which are responsible for approximately 70% of cervical cancers.¹ The nonavalent vaccine covers an additional five oncogenic types responsible for another 20% of cervical cancers.⁵ HPV vaccination is recommended for girls aged 11–12 years, with catchup vaccination up to 26 years. Nationwide in 2015, a total of 63% of girls aged 13–17 years had received at least one dose of the HPV vaccine.⁶

Prior studies on the HPV vaccine have investigated the vaccine’s impact on the prevalence of the virus and high-grade cervical lesions.7, 8, 9, 10, 11 To date, no study has examined trends in cervical cancer incidence before and after the HPV vaccination was introduced among young females who may have been vaccinated. An ecologic study comparing cervical cancer incidence among young females before and after HPV vaccine introduction provides insight into whether HPV vaccination has contributed to potential changes in cervical cancer incidence, particularly among younger girls who may not routinely undergo screening to detect cervical lesions.12, 13, 14 The objective of this study is to compare cervical cancer incidence by histology between the pre-vaccine and vaccine eras among young women (aged 15–24 years and 25–34 years) using data from U.S. Cancer Statistics (USCS), the combined data from the Centers for Disease Control and Prevention (CDC) National Program for Cancer Registries (NPCR) and the National Cancer Institute (NCI) Surveillance, Epidemiology, and End Results (SEER) Program. To explore the relationship between HPV vaccination and changes in cervical cancer incidence, as secondary aims, this study also assesses HPV vaccine uptake, HPV infections, and changes in cervical cancer screening guidelines.