BACKGROUND AND PURPOSE:

• Only approximately 50% of adolescents in the US. have completed the full HPV vaccine series
  • About 68% received at least one dose
  • Current trials are investigating the efficacy of a single dose regimen
• Sonawane et al. (JAMA Network Open, 2019) assessed HPV infection prevalence and association of number of vaccine doses

METHODS:

• Cross-sectional study
• Data sources (2009 to 2016)
  • National Health and Nutritional Examination Survey (NHANES)
• Participants
  • Women
  • 18 to 26 years
  • HPV vaccination and HPV test information available (i.e., no missing data)
  • Immunization history: Self-reported and collected by trained interviewers
  • Sexual behavior data: Self-reported
  • Cervicovaginal swab specimens: Obtained by patients and tested  
• Study design and data analysis
  • Designed to examine the difference in the prevalence of HPV infection by number of doses received
  • Probability estimates for HPV types 6, 11, 16, and 18 generated based on number of vaccine doses and risk factors

RESULTS:

• 1,620 women
  • Mean age: 22.2 years | 56.5% white
  • Unvaccinated: 1004 women
  • ≥1 dose of HPV: 616 women
    • 1 dose: 106 women
    • 2 doses: 126 women
    • 3 doses: 384 women
• Infection with HPV type 6, 11, 16, or 18 was significantly less prevalent among women who received any number of HPV doses
  • Unvaccinated women: 12.5% (95% CI, 9.7% to 15.3%)
  • 1 dose: 2.4% (95% CI, 0% to 4.9%)
  • 2 doses: 5.1% (95% CI, 0.8% to 9.5%)
  • 3 doses: 3.1% (95% CI, 0.9% to 5.3%)
• There was no significant difference in prevalence for
  • 1 dose vs 2 doses
  • 1 dose vs 3 doses
• Predicted probability of infection with HPV 6, 11, 16, or 18 was higher in unvaccinated women
  • Unvaccinated women: 7.4% (95% CI, 7.1% to 7.7%)
  • 1 dose: 2.3% (95% CI, 1.9% to 2.8%)
  • 2 doses: 5.7 (95% CI, 5.1% to 6.2%)
  • 3 doses: 3.1% (95% CI, 2.9% to 3.4%)
• Black women had a greater predicted probability (10.8%) of infection with HPV type 6, 11, 16, or 18 compared with white women (6.6%)
• Predicted probability was also higher for women with more than 5 lifetime male sexual partners (11.6%) than women with 0 to 5 lifetime male partners (3.3%)

CONCLUSION:

• Realistically, adolescents may not always complete the HPV vaccine series, for reasons including health insurance issues
• The authors recognize limitations of the study including self-reporting
• This study demonstrates that 1 dose of the HPV vaccine may result in similar protection compared to additional doses
• The authors state

If ongoing trials confirm sufficient efficacy and sustained duration of protection from a single-dose regimen, vaccine initiation (as opposed to the series completion) will become a more achievable metric of population coverage

Learn More – Primary Sources:

Prevalence of Human Papillomavirus Infection by Number of Vaccine Doses Among US Women

Related ObG Topics:

HPV Vaccines: Cochrane Reviews Looks at the Evidence with Multi-Year Follow-Up

The HPV Vaccine Leads to a Reduction in Cervical Precancers in Young Women in the U.S.

How has HPV Prevalence Changed Since Introduction of Vaccine?