Study suggests greater HPV vaccine uptake reduced infection rates in women born in 1990s

Women born in the 1990s had a significantly lower HPV infection rate compared with those born a decade earlier — a finding that allowed researchers to connect greater HPV vaccination coverage with direct protection and herd immunity.

According to the study, published in JAMA Health Forum, the CDC Advisory Committee on Immunization Practices first issued a recommendation that girls and women aged 9 to 26 years routinely be vaccinated against HPV in 2006.

“Steady improvements in HPV vaccination coverage during the past decade may have translated into protective benefits among the contemporary birth cohort (ie, women born in the 1990s compared with the 1980s),” Zahed Shahmoradi, PhD, a postdoctoral research fellow at The University of Texas Health Science Center in Houston at the time of the study, and colleagues wrote. “To measure whether HPV vaccination has been associated with reduced infection rates among recently born vaccinated women (vaccine-mediated immunity) and unvaccinated women (herd protection), we compared HPV prevalence in the 1980s vs. the 1990s birth cohorts and a pre-vaccination period vs. a recent period.”

Shahmoradi and colleagues estimated the prevalence of HPV types 16 and 18 — two of the most common types associated with cervical cancer — for 2,698 women born in the 1980s and the 1990s using data collected in the National Health and Nutritional Examination Survey. Specifically, they focused on the NHANES 2005 to 2006 (pre-vaccine introduction period) and the 2015 to 2016 (recent period) cycles, which were used to estimate vaccine effectiveness in those periods.

In total, 55% of women aged 18 to 20 years, 52% of those aged 21 to 23 years and 50% of those aged 24 to 26 years during the NHANES 2015 to 2016 cycle had received at least one dose of the HPV vaccine.

In an analysis of women aged 18 to 32 years, the Shahmoradi and colleagues determined the 1990s cohort had a significantly lower prevalence of HPV infection with types 16 and 18 compared with the 1980s cohort (5.6% vs. 12.5%).

Separately, the researchers analyzed women born in the 1980s and 1990s when they were aged 18 to 26 years. They found that 15.2% of women in this age group during the first cycle of the NHANES — who were born in the 1980s — had an HPV infection. However, only 3.3% of those in the recent NHANES cycle — who were born in the 1990s — had an infection, with 5.1% of unvaccinated women and 1% of vaccinated women in the second cycle having an infection. Notably, women aged 18 to 20 years during the 2015 to 2016 cycle had an infection rate of 0%.

The estimated likelihood of having an HPV infection was significantly lower for women born in the 1990s vs. 1980s (6.3% vs. 13.6%). The likelihood of infection was also lower during the most recent NHANES cycle compared with the first cycle (3.5% vs. 15.7%), with unvaccinated and vaccinated women in the 2015 to 2016 cycle having a 60% and 92% lower risk for infection, respectively, compared with their counterparts in the earlier cycle.

“A larger decline in the prevalence of HPV-16/18 infection among 18- to 20-year-old women during the 2015 to 2016 time period may reflect greater direct and herd protection from broader HPV vaccination coverage,” Shahmoradi and colleagues wrote.