1. Within 4 years of vaccine introduction, the prevalence of vaccine-type HPV strains (6,11,16,18) decreased by 56% in girls ages 14-19.
2. In the entire study population (women ages 14-59), the estimated vaccine effectiveness of at least 1 dose was 82% (95% CI, 53-93).
Evidence Rating Level: 2 (Good)
Study Rundown: This study found that 4 years after vaccine introduction, the prevalence of vaccine-type HPV strains (6, 11, 16, 18) decreased by 56% in a large, nationally representative sample of girls ages 14-19. Given that only 34% of participants in this age group reported receiving at least 1 HPV vaccine dose, these results suggest that the HPV vaccine is highly effective. Additionally, across all participants (women ages 14-59), the estimated vaccine effectiveness of at least 1 dose was 82% (95% CI, 53-93).
While the magnitude of the decrease is impressive, results may be limited by selection bias, particularly given the self-collection of specimens. Strengths include a nationally representative sample population and thorough evaluation of HPV infection by linear array. Further research might assess long-term immunity at 10 or even 20 years post-vaccination (stratified by receipt of 1 dose, 2 doses, or the complete 3-dose series), particularly given the rising age of first marriage in the U.S.
In-Depth [cross-sectional study]: Researchers from the CDC used data from the 2003-2010 National Health and Nutrition Examination Surveys (NHANES) to compare the prevalence of HPV infections in women ages 14-59 years in the pre-vaccine era (2003-2006) and the post-vaccine era (2007-2010). HPV infection was determined by analysis of self-collected cervicovaginal swab specimens.
A total of 4,150 participants from the 2003-2006 survey (83% of participants) and 4,253 participants from 2007-2010 (87% of participants) submitted adequate samples and were included in the analysis. In girls ages 14-19, the prevalence of HPV infection from any strain dropped 21% (PR=0.79, 95% CI=0.66-0.95) after vaccine introduction, falling from 32.9% pre-vaccine to 26.1% post-vaccine. In the same age group, the prevalence of vaccine type HPV (6, 11, 16, 18) decreased by 56%(PR=0.44, 0.31-0.62), from 11.5% to 5.1%. Across all age groups, the estimated vaccine effectiveness of at least 1 dose was 82% (95% CI, 53-93).
By Maren Shapiro and Leah Hawkins, MD, MPH
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