Doctor's recommendation was associated with vaccine initiation, but only in bivariate analyses (Table 3). At baseline, few parents revealed that a health care provider had recommended they get HPV vaccine for their daughters (22%, 153/650). About half of parents who had received a doctor's recommendation but had not acted on it before the baseline interview did so during follow-up (51%, 46/94) compared to 21% (103/473) of parents who had not received a recommendation before the baseline interview. Parents of all but a few daughters who had not initiated HPV vaccination at baseline reported they had been to their doctor between baseline and follow-up (97%, 533/563; data not available for 4 parents). Of these parents, 28% (145/533) had initiated vaccination for their daughters by follow-up. Of the remaining parents, only 1 in 3 reported receiving doctors' recommendations for HPV vaccine (37%, 122/388), suggesting missed opportunities.
In multivariate analyses, parents were more likely to have gotten the vaccine for their daughters if they anticipated greater regret if not vaccinating did not protect their daughters from HPV infections (RR = 1.85, 95% CI = 1.13–3.02) (Table 5). Not initiating the vaccine was associated with being a born again Christian (RR = 0.53, 95% CI = 0.39–0.74), perceiving greater barriers to getting the vaccine (RR = 0.57, 95% CI = 0.39–0.83) or reporting that needing more information was the main reason for not having vaccinated at baseline (RR = 0.41, 95% CI = 0.22–0.76). Removing intentions from the multivariate model did not affect any variable's level of statistical significance. Perceived likelihood did not interact with perceived severity to predict vaccine initiation (data not shown, P = 0.96).
Post hoc analyses of the 5 items in the perceived barriers scale found that parents who reported their daughters had received at least 1 dose of HPV vaccine said it would be somewhat or very hard to find a provider or clinic that stocked the vaccine (4%, 11/149) less often than parents who reported their daughters had received no vaccine doses (14%, 45/418, P < 0.05). Vaccinators also said it would be hard to find a provider or clinic where the vaccine would be affordable (20%, 41/149) less often than parents who reported their daughters had received no vaccine doses (35%, 143/418, P < 0.05). Vaccine uptake was not associated with the remaining perceived barriers items (finding a provider or clinic that is easy to get to, finding a provider or clinic that has convenient appointments, and being able to pay for the vaccine).
In this longitudinal study, predictors of HPV vaccine initiation among adolescent girls differed from those suggested by HPV vaccine acceptability studies conducted primarily before vaccine licensure.10 Many health belief model constructs that we expected would be associated with uptake were not. Instead, key predictors of initiation included anticipated regret if their daughters got HPV that the vaccine could have prevented as well as not being a born-again Christian. While many studies have examined interest in a hypothetical HPV vaccine or cross-sectional correlates of vaccine initiation,10–13,18 this study adds important new information on predictors over time.
Over 2 years after HPV vaccine became available to the public, only about 1 in 3 eligible girls in an area with elevated cervical cancer rates had initiated the vaccine. This vaccine uptake is similar to that found in other US studies from the same time period.7 It is also similar to coverage for another adolescent vaccine (tetanus, diphtheria, acellular pertussis vaccine) about 2 years after its introduction in the United States (30% in 2007).7,19 Our findings suggest missed opportunities to increase HPV vaccine uptake, including a large percentage of daughters who had been seen by their doctors but had not received an HPV vaccine recommendation, and two-thirds of parents who intended to vaccinate their daughters but had not followed through with these plans a year later. One positive finding was parents' report that most girls who had received the vaccine were on schedule to receive their next dose or had received all 3 doses.
In contrast to what we previously found in cross-sectional analyses of our baseline data on uptake11 and in our systematic review of acceptability,10,12 HPV vaccine initiation was not longitudinally associated with key health belief model constructs (perceived risk, perceived severity, and physician recommendation as a cue to action). The small and not statistically significant associations with risk beliefs were within the range we observed in our previous meta-analysis of vaccine use among adults.20 However, the observed associations were much smaller than associations with anticipated regret from not vaccinating. While the special predictive power of anticipated regret from not vaccinating mirrors the findings of Weinstein et al.,21 we additionally show that anticipated regret from vaccinating, at least about sexual disinhibition, played essentially no role in vaccine decisions. This finding may be due to the different outcomes (cervical disease vs. sexual disinhibition), or it may reflect different beliefs about harms caused by action and inaction.22
Doctor's recommendation predicted reported HPV vaccine initiation in bivariate analyses, which is consistent with previous findings that doctors are uniquely credible and persuasive on issues related to medical care.23,24 The nonsignificant multivariate association may underestimate the importance of doctors' recommendations, because our longitudinal analyses evaluated vaccine initiation over time according to doctors' recommendations assessed at the baseline interview. As analyses only included those not yet vaccinated at baseline, daughters with doctor's recommendations were those who had gotten a recommendation before baseline, but had not acted on it, and thus were perhaps less likely to be vaccinated later. Physicians could play a larger role in encouraging HPV vaccine initiation by adolescent girls and in providing information about the vaccine to parents.
Uptake was lower among parents who said they needed more information about the vaccine. Messages from doctors or other respected professionals that focus on helping parents who already plan to act and reducing perceived barriers may be especially effective in increasing HPV vaccine uptake. Conversations about consequences of vaccination, such as potential side effects, may be better redirected to focus on the consequences of not vaccinating (e.g., anticipated regret). Simply imagining—and anticipating regretting—a future in which their daughters had HPV was a powerful motivator for parents.
Born-again Christian parents in our study were half as likely as other parents to get their daughters HPV vaccine. This is especially concerning, given that as many as 34% of the US population identify themselves in this way.25 A study in California found that born-again and evangelical Christian parents were less likely than other parents to prefer to vaccinate their daughters before age 13 than at older ages,26 but the study did not address the more fundamental question of willingness to get the vaccine at all or vaccine uptake. Our findings suggest public health programs to increase HPV vaccine uptake should make special efforts to reach born-again Christian parents.
Importantly, we found no differences in vaccine initiation by race, urbanicity, or age group. Given that the risk of dying from cervical cancer in the US is about twice as high for black women as for white women, equivalent but low uptake by blacks and whites may not be sufficient to reduce racial disparities.1 Additional efforts should focus on ensuring that HPV vaccine uptake is high across all groups, but these efforts should especially focus on those at highest risk. We previously reported higher uptake among older teens in analyses of our baseline data.27 The different findings might reflect a previous desire to catch up older teens to recommended vaccine guidelines or parents now being more comfortable with recommendations to vaccinate younger adolescent girls. Because HPV vaccine is likely to be most effective if given before adolescent girls initiate sexual activity, it may even be preferable to have higher rates of uptake for younger aged adolescent girls.
Study strengths include a diverse, population-based sample of parents from high-risk areas. The study's longitudinal design is also a strength, although we cannot completely rule out confounding by unmeasured variables. Limitations include the use of parent self-report to assess HPV vaccination of their female daughters. While studies have not yet examined accuracy of self-reported HPV vaccine initiation, adults' self-report of having received influenza vaccine is reasonably sensitive and specific.28,29 The generalizability of the findings to other populations is not yet known.
HPV vaccine research is important in groups at highest risk for cervical cancer, including blacks and Hispanics who have high cervical cancer rates and people living in rural areas with diminished access to care. In this high risk population, we found that many parents' intentions to vaccinate were unrealized, and doctors frequently missed opportunities to recommend HPV vaccine at clinic visits. Our study's findings suggest correlates of uptake (for example, anticipated regret) that offer novel opportunities for interventions designed to increase vaccine uptake in these and likely other populations.
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