Executive Summary

Public health programs that devote a portion of their funding to encourage more boys to be vaccinated against human papillomavirus (HPV), rather than merely attempting to raise coverage among girls, ultimately might protect more people for the same price, a new analysis indicates.

  • The incidence of new HPV-related cancer cases in the United States in 2009 exceeded 35,000, with more than one-third of cases occurring in the male population.
  • Even with recommendations that boys and girls ages 11 to 12 should receive the HPV vaccine, just 37% of girls and 14% of boys in the United States have received all three shots in the HPV vaccine series.

Public health programs that devote a portion of their funding to encourage more boys to be vaccinated against human papillomavirus (HPV), rather than merely attempting to raise coverage among girls, ultimately might protect more people for the same price, a new analysis indicates.1

The incidence of new HPV-related cancer cases in the United States in 2009 exceeded 35,000, with more than one-third of cases occurring in the male population.2 It is estimated that almost all cervical cancers, up to 90% of anal cancers, and up to 60% of oropharyngeal cancers are caused by HPV.3 While screening has led to a significant decrease in cervical cancer incidence and mortality in developed countries, there has been an increase in other HPV-related cancers for which population screening is not performed.4

Many HPV cancers could be prevented with vaccination. However, even with the Centers for Disease Control and Prevention’s recommendations that boys and girls ages 11 to 12 should receive the HPV vaccine, just 37% of girls and 14% of boys in the United States have received all three shots in the HPV vaccine series.5 (Contraceptive Technology Update reported on the statistics. See the article, “HPV vaccine continues to be underutilized,” October 2014.)

Analysis eyes strategies

It remains debated among experts whether HPV vaccination programs should focus on girls only or whether boys and girls should be targeted simultaneously, says Marc Ryser, PhD, a mathematician at Durham, NC-based Duke University. Previous modeling studies that addressed this question deemed it more effective to focus on females only, notes Ryser.

One common assumption among these modeling studies was that it would be possible to vaccinate a large fraction of females, says Ryser, who served as lead author of the current analysis. However, although high uptake among girls has been achieved in other countries such as the United Kingdom, the HPV vaccine has only had limited success in the United States, he notes.

In fact, the fraction of girls who have received all three doses has stagnated around 37%, and the fraction of fully vaccinated boys remains low at about 14%. At the same time, parental opposition to getting their children vaccinated against HPV has increased to about 44%.6

“Together, stagnating vaccine uptake at low levels and increasing parental opposition seem to suggest that a further increase in uptake may require costly outreach and education programs to raise awareness and acceptability of the vaccine,” says Ryser. “In addition, we expect that it is more expensive to raise the uptake from 37% to 38% than from 14% to 15%. The higher the uptake, the harder it is to find additional parents who are willing to vaccinate their child. In other words, educational costs are expected to be coverage-dependent.”

To find out whether different strategies for allocating public funds might protect more people, Ryser, Duke mathematician Kevin McGoff, PhD, obstetrician/gynecologist Evan Myers, MD, MPH, and colleagues developed a mathematical model of HPV transmission among sexually active 14-18 year olds. The goal of the study was to assess the impact of education and outreach costs on the optimal vaccination strategy.

The findings suggest that public health officials might be able to protect more people for the same price by shifting some funds to encourage vaccination of boys, since the fraction of parents willing to vaccinate has yet to be exhausted among boys.1

What’s the next step?

What do the Duke analysts see as the next step in research in determining real-world data on actual patient costs? The costs, and how to measure them, will depend based on the intervention, says Myers.

If the intervention involves providers spending a little bit more time with parents, there are ways to measure the actual time being spent discussing vaccines, Myers states. Measuring such methods might be difficult, with data relying on provider self-report or having someone sitting in the office with a stopwatch, he observes.

“If it’s a specific advertising/outreach campaign, the costs of designing and implementing those types of interventions are measurable and would be part of the budgeting process for any study,” says Myers.

REFERENCES

  1. Ryser MD, McGoff K, Herzog DP, et al. Impact of coverage-dependent marginal costs on optimal HPV vaccination strategies. Epidemics 2015; 11:32-47.
  2. Jemal A, Simard EP, Dorell C, et al. Annual report to the nation on the status of cancer, 1975-2009, featuring the burden and trends in human papillomavirus (HPV)-associated cancers and HPV vaccination coverage levels. J Natl Cancer Inst 2013; 105(3):175-201.
  3. Crow JM. HPV: The global burden. Nature 2012; 488(7413):S2-S3.
  4. Simard EP, Ward EM, Siegel R, et al. Cancers with increasing incidence trends in the United States: 1999 through 2008. CA — Cancer J Clin 2012; 62(2):118-128.
  5. Stokley S, Jeyarajah J, Yankey D, et al. Immunization Services Division, National Center for Immunization and Respiratory Diseases, CDC. Human papillomavirus vaccination coverage among adolescents, 2007-2013, and postlicensure vaccine safety monitoring, 2006-2014 — United States. MMWR 2014; 63(29):620-624.
  6. Darden PM, Thompson DM, Roberts JR, et al. Reasons for not vaccinating adolescents: National Immunization Survey of Teens, 2008-2010. Pediatrics 2013; 131(4):645-651.

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