HPV detection declined in young women after the introduction of HPV 4-valent and 9-valent vaccine during a >10-year period — even among those who were unvaccinated, researchers found.
From 2006 to 2017, rates of 4-valent and 9-valent vaccine-type HPV had significant declines among both vaccinated and unvaccinated young women ages 13 to 26, reported Jessica Kahn, MD, of the University of Cincinnati in Ohio, and colleagues, in Pediatrics.
They argued that research has shown that the effectiveness of HPV vaccines in community settings could be lower because “women in the community may have been infected with vaccine-type HPV before vaccination and may have lower compliance with the vaccination series or be less healthy than those in the clinical trials.”
“Assessments of vaccine effectiveness and herd protection are essential to guide public health messaging, clinical counseling, vaccination recommendations, and cervical cancer screening recommendations,” they argued.
Researchers examined a cohort of young women, ages 13 to 26, who were recruited from hospital-based health clinics over a period of 11 years for four surveillance studies. Patients were eligible for participation if they were sexually experienced. Researchers added that they “determined the proportion of vaccinated and unvaccinated women who were positive for vaccine-type HPV across the studies.”
Cervicovaginal swabs were collected by self-swab or clinician swab from each participant, the authors said. Vaccination status was defined as receipt of one or more HPV vaccine doses before enrollment, as assessed by the Ohio statewide immunization registry.
Overall, there were 1,580 participants, with a range of mean ages from all four studies of around 19. Around 70% to 77% of participants identified as African American or multiracial, and about 50% to 56% said they had two or more male lifetime sexual partners.
HPV vaccination rates increased from 0% to 84% over the course of the four studies, with 97% of study participants receiving the 4-valent vaccine. Among young women who received the vaccine, rates of 4-valent vaccine-type HPV declined from 35% to 6.7%. But rates of 4-valent vaccine-type HPV among unvaccinated women also exhibited substantial declines — dropping from 32.4% to 19.4%.
Proportions of vaccinated women with one or more of the five HPV types in the 9-valent vaccine, but not the 4-valent vaccine, also declined from 23.4% to 7.3%, but there was an increase in the portion of unvaccinated women with one or more of these five HPV types (from 22.9% to 36.1%), the authors said.
Vaccination effectiveness was 90.6% in wave 3 of the study, but 80.1% in wave 4 versus wave 1, they added.
This was a noteworthy finding of the study, stated Amanda F. Dempsey, MD, of the University of Colorado Denver in Aurora, in an accompanying editorial.
“This definition [of vaccination as ≥1 dose of vaccine] suggests that some, or maybe even many women in the cohort had not received the 3 doses recommended for full protection … [and] makes the high vaccine effectiveness reported actually quite remarkable and adds further evidence that this vaccine is highly protective,” she wrote.
Moreover, Dempsey said that the adjusted odds of women vaccinated with the 9-valent HPV vaccine being infected with these five additional HPV types ranged from 0.22 to 0.48.
“Evidence of cross protection is important with the recent transition to the 9-valent vaccine in the United States because many women question whether there is a benefit to being revaccinated with the 9-valent vaccine after having completed the full course of the quadrivalent vaccine when they were younger,” she wrote, adding that there is “no specific recommendation” from CDC Advisory Committee on Immunization Practices to get the 9-valent vaccine after receiving the 4-valent vaccine.
A study limitation was the small portion of women who received the 9-valent vaccine in wave 4, which limited the ability of the authors to examine trends in HPV prevalence due to the effects of the 9-valent vaccine. They also noted results may not be generalizable to the general U.S. population.
This study was supported by the National Institute of Allergy and Infectious Diseases and the National Center for Advancing Translational Sciences, and was funded by the NIH.
Spinner disclosed no relevant relationships with industry. Co-authors disclosed support from Merck, and relevant relationships with Roche, BD, Abbott, Merck, and GlaxoSmithKline. One co-author disclosed serving as co-chair of a study of HPV vaccines in men with HIV that was funded by the NIH and to which Merck provided vaccine and serology testing.
Dempsey disclosed relevant relationships with Merck, Sanofi, and Pfizer.