HPV Rates Continue to Decline, New Data Suggest Herd Immunity Growing

The introduction of the human papillomavirus (HPV) vaccine has led to a dramatic reduction in the prevalence of HPV among young adults, according to a major new study published today in Annals of Internal Medicine.

This report shows the benefits of vaccination extend beyond the vaccinated population, resulting in a significant drop in HPV prevalence even among people who did not get the vaccine.

“Twelve years into the United States’ HPV vaccination program, national data demonstrate an increasing impact among females, strong herd effects among unvaccinated females in the context of increasing HPV vaccination coverage among both males and females, and greater percentages of persons receiving the HPV vaccine in early adolescence before HPV exposure through sexual contact,” wrote the authors.

HPV is the most common sexually transmitted infection in the United States, they noted. Although most people with HPV do not have symptoms and may not know they are infected, tens of thousands develop HPV-associated cancers each year, including cervical, anogenital, or oropharyngeal cancers.

The HPV vaccine was first introduced in the United States in 2006. Initially, the quadrivalent vaccine (4vHPV) was recommended for females aged 11 or 12 years and for women up through age 26 for “catch-up” vaccination. In 2011, the vaccine recommendation was extended to males. In 2015, a 9-valent version of the vaccine was introduced.

The new study was designed to evaluate real-world evidence of the effectiveness of the vaccine program, and the authors used data from the National Health and Nutrition Examination Survey (NHANES), an ongoing cross-sectional survey conducted by the CDC and released in 2-year cycles. They looked at 4 time frames to see how the vaccine has changed HPV prevalence over time: 2003 to 2006 (the prevaccine era), 2007 to 2010, 2011 to 2014, and 2015 to 2018. Their data focused on sexually experienced people aged 14 to 24 years.

The data showed vaccine coverage rates were increasing, although they are still below those of other adolescent vaccines. As shown by the 2007 to 2010 data set, just a quarter of sexually experienced females aged 14 to 24 years had received the vaccine. However, by 2015 to 2018, that rate had grown to 59%. Among males, 27% of sexually experienced males had received the vaccine in the 2011 to 2014 data set, and that number grew to nearly 50% by 2015 to 2018.

The data also show that rising vaccination rates led to a major downward trend in the number of infections with the 4 types of HPV targeted by the original 4vHPV vaccine.

“By 2015-2018, compared with the prevaccine era, 4vHPV-type prevalence declined 85% overall among sexually experienced 14- to 24-year-old females, 90% among vaccinated females, and 74% among unvaccinated females,” the investigators found.

Similar declines among the types of HPV not covered by the vaccine were not seen.

The authors calculated a vaccine effectiveness rate of 60% to 84% for females over the course of the vaccine era, and 51% for males between 2013 and 2016. They said the data suggest unvaccinated people are benefiting from herd immunity, and that this finding aligns with reports from other countries with similarly low vaccination rates.

An accompanying editorial notes that the data are encouraging and show that the vaccine is working. However, the authors also warned that the COVID-19 pandemic has led to decreased rates of vaccination, including against HPV, that have created a need for providers to help patients catch up. Research has identified several strategies physicians can use to boost vaccination, including telling parents that their child is due for vaccination at the current visit. The editorial’s authors said vigilance is required to ensure the benefits of the vaccine continue.

“Using evidence-based methods and redoubling our efforts to prioritize HPV vaccination will be crucial to ensuring that we do not lose a generation to preventable HPV-associated cancer,” they wrote.

Reference

Rosenblum HG, Lewis RM, Gargano JW, Querec TD, Unger ER, Markowitz LE. Human papillomavirus vaccine impact and effectiveness through 12 years after vaccine introduction in the United States, 2003 to 2018. Ann Intern Med. Published online May 16, 2022. doi:10.7326/M21-3798