Two to five months following recommendations for HPV vaccination of women, the CDC reported that only 10% of 18-26 year olds had initiated the vaccine series.[14
] Results of our study, which assessed HPV vaccination among 19-26 year old women seen in a university-based primary care clinic system 2 ½ years after the vaccine was available, suggest that HPV vaccine uptake among young adult women continues to be low. Only 18% of these women had initiated the 3-dose series and only 10% of the cohort with ≥1 year of study eligibility had received all three vaccine doses within the 30 month period. HPV vaccination use among adult women is notably lower than adolescents seen in the same clinical system. In a previous analysis that assessed within the same clinical setting HPV vaccination among adolescent female 15 months
after the vaccine was available we found that 28% of 11-17 year olds had initiated the vaccine series and 15% of the cohort with ≥1 year of study eligibility had received all three vaccine doses.[3
Among adolescents, national and regional assessments have demonstrated disparities in HPV vaccine utilization by race, age, insurance and poverty level.[3
] Similar findings have not been confirmed nationally for adult women, but have been supported by regional analyses [4
] and are also supported by our results. Our study is one of the first to demonstrate disparities in adult HPV vaccine uptake by medical specialty, and to describe differences in these disparities by different doses in the series. Our longitudinal analyses also present evidence to suggest that the race- and insurance-related disparities in HPV vaccine use are worsening over time.
In our study African American race was associated with increased
vaccine series initiation but decreased
receipt of second and third doses when compared to whites and those of other/unreported race. These results are similar to our previous study of adolescent HPV vaccine utilization within the same university-based clinical system and to other studies.[3
] The consistency across the age spectrum of lower series completion among African Americans is concerning given that minority women are at increased risk of HPV-related morbidity and mortality.[23
] Lower utilization of both Pap testing and HPV vaccination among minority women suggests that cultural mediators may create barriers to participation in these important preventive activities. It also raises the broader question of whether HPV vaccination efforts as they currently stand will have any impact on population-level rates of cervical cancer in the U.S. It appears that additional work is needed to identify culturally relevant educational messages and interventions that can improve compliance with both HPV vaccination and Pap smear screening among this population.
Disparities in vaccine uptake among young adult women with regard to age and insurance type were also identified in this study. Younger age was associated with an increased odds of starting the vaccine series but age had no association with completing the series once it had begun. One explanation for this age effect is women may believe it is “too late” for them to benefit from HPV vaccination as they age and become more sexually experienced.[25
] In our previous study of adolescents[3
] a reverse association with age was found – younger adolescents were less likely to initiate the series when compared to older adolescents (with no associations between age and second/third doses). Taken together these results suggest that age primarily affects the decision of whether or not to vaccinate, not the ability or willingness to comply with subsequent doses once the vaccine series is begun. Interventions that target series initiation may therefore be an effective “starting point” to improve HPV vaccine uptake. However, it is important to note that the women completing the vaccination series in this study deviated significantly from the ideal schedule used in HPV vaccine efficacy trials.[26
] Theoretically, this deviation could reduce the efficacy of the vaccine, though this hypothesis remains to be proven.
For women >18 years old, it is important to consider any age effects on vaccine uptake in the context of insurance status. Individuals >18 years old are not eligible for the Vaccines For Children (VFC) program, a federally funded program that provides free vaccines to millions of under or un-insured individuals ≤18 years of age.[27
] In addition, between the ages of 19-26 years coverage under parents' insurance plans also declines, often without replacement by employer-sponsored individual health coverage.[28
] These age-based differences in insurance status could explain, at least in part, the finding of lower vaccine series initiation with advancing age among young adult females in our study. However, only a small proportion of women in our study were without insurance, and the majority of private and public payers were covering the HPV vaccine for adult women at the time of the study.
This study also demonstrated disparities in HPV vaccine use by medical specialty. FM providers were substantially more likely to initiate the vaccine series, and to use “problem-focused” visits to administer vaccine doses than the other medical specialties. In addition, there were specialty-based differences in series initiation but not series completion – a finding that has also been described for HPV vaccination among adolescents.[3
] One explanation for this finding is that, because they care for children (who require many vaccines), FM providers may be more adept or comfortable than gynecologists or GM providers at convincing adult patients to receive the HPV vaccine. Anecdotal reports from our institution suggest that gynecologists might have a particularly difficult time in initiating the series because some patients believe their insurance company will deny coverage of the vaccine since the gynecologist is not designated as their “primary care provider.” The lack of specialty-based differences in administration of 2nd
doses again highlights the importance of vaccine series initiation. Importantly, “missed opportunities” for providing vaccines were commonplace across all medical specialties.
Thus study's results should be interpreted in light of several important limitations. First, the study population was limited to one university-based health system located in Michigan. Though this population is both economically and racially diverse, results may not be generalizable to other geographic locales, to patients seen in private practice or public health settings, or to non-medical-based populations. Furthermore, Latino ethnicity, a variable that has been shown to be associated with differences in vaccination levels for childhood vaccines[30
], could not be assessed in our analysis. In other studies of HPV vaccination, Latina ethnicity has been associated with increased series initiation, but decreased series completion for HPV vaccines.[11
] Second, the sample included very few individuals without health insurance. Young adults have higher rates of un-insurance when compared to other ages[28
] and the high out-of-pocket costs of HPV vaccines likely prevent many without insurance from being vaccinated. Thus at a population level, HPV vaccination uptake among 19-26 year old females is expected to be lower than that found in this study. Third, the analysis did not capture doses of vaccine provided outside of the university setting, though our results appear generally consistent with other studies on HPV vaccine uptake among adults.[14
] Fourth, we were unable to discern reasons why vaccination did not occur among eligible patients. Some patients may have been offered the vaccine and refused. In addition, inconsistency in provider recommendation could have caused variability in uptake between different clinical settings or among different patient populations.
Clinicians caring for women and men eligible for the HPV vaccine need to explore options to promote the initiation of the vaccine at every encounter with patients. Once the vaccination series is started, then systems need to be tested which achieve completion of the series in the ideal time intervals. In the era of electronic medical records, systematic prompts to clinicians, support staff, and patients could significantly improve this process.