1. The human papillomavirus (HPV) vaccine has been shown to be effective in protecting against quadrivalent HPV vaccine (4vHPV)-type infections in the United States.
2. The impact of the vaccine on reducing HPV prevalence was further potentiated by herd immunity.
Evidence Rating Level: 1 (Excellent)
Study Rundown: HPV is the most common sexually transmitted infection in the United States. Long-term infection of oncogenic subtypes can lead to cervical, anorectal, and oropharyngeal cancers, while non-oncogenic subtypes can cause anorectal warts. The first approved and broadly recommended HPV vaccine was quadrivalent (4vHPV), targeting the oncogenic HPV 16 and 18, and the non-oncogenic HPV 6 and 11. Subsequently, a 9-valent vaccine was also introduced to include five other oncogenic subtypes. Prevalence monitoring of the original 4 HPV subtypes is ongoing and helps evaluate the vaccine impact. The current study utilized the National Health and Nutrition Examination Survey (NHANES) data to estimate the vaccine’s effectiveness against 4vHPV-type infections among sexually active U.S. individuals. The study examined prevalence rates before and after vaccine introduction, as well as between vaccinated and unvaccinated individuals. The vaccine was associated with declining prevalence rates of 4vHPV-types among males and females, both vaccinated and unvaccinated, in contrast to non-4vHPV-types. Despite the limitations of self- or parent-reported data and small numbers of certain HPV subtypes, the vaccine program was shown to be effective in reducing the prevalence of targeted HPV subtypes, an impact enhanced by herd immunity.
In-Depth [cross-sectional study]: The present study reported the results from the ongoing NHANES between 2003-2006 (pre-vaccine era) and 2007-2010, 2011-2014, and 2015-2018 (vaccine eras). NHANES is an ongoing, nationally representative survey study of the U.S population. Sexually active participants aged 14 to 24 years were included. Cervicovaginal and penile specimens were collected for HPV DNA testing and genotyping. The impact of the HPV vaccine on infection was assessed by comparing prevalence between vaccinated and unvaccinated individuals, and between the pre-vaccine and vaccine eras. The study population included 3,197 female and 661 male participants. Overall, the proportion of female participants reporting having received at least one HPV vaccine dose was 25.2% in 2007-2010 and increased to 59.0% in 2015-2018. For male participants, the proportion of 14.1% in 2011-2014 and increased to 29.5% in 2015-2018. When compared to pre-vaccine era, the vaccine impact on 4vHPV-type prevalence in 2015-2018 was 85% overall – 90% among vaccinated female participants (Prevalence Ratio [PR], 0.10; Confidence Interval [CI], 0.04 to 0.28), and 74% among unvaccinated females participants (PR, 0.26; CI, 0.12 to 0.57). This contrasted with the absence of significant reductions in the non-4vHPV-type prevalence. Notably, the vaccine impact observed among unvaccinated female participants indicated the considerable role herd immunity played in protecting against HPV infection. Study limitations included the self- or parent-reported data, and the small numbers of certain HPV subtypes. Overall, the study demonstrated the impact of vaccination on HPV prevalence and emphasized the contribution of herd immunity.
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