The implications of this study must be considered in the context of several limitations. The opinions recorded in this survey, for example, are not necessarily representative of those of the entire target population, because of a potential response bias towards non-compliant patients. The response rate of 16.1% was rather low and was lower than that of the vaccinated subgroup (28%) [
17]. In addition, more than 80% of respondents were white and all study subjects had access to health care and were insured. The results regarding intent to get vaccinated, while interesting, may not ultimately reflect future behavior. For instance, a meta-analytic review of Theory of Planned Behavior research reported a relative modest average correlation of 0.47 between intentions and subsequent health behaviors [
18].
Although the majority of unvaccinated respondents in this study recognized the potential impact of cervical cancer and genital warts, only about one in three considered vaccination against HPV to be important to them. Half of respondents reported being very or extremely likely to discuss the vaccine with a doctor but almost half (48.1%) were at least somewhat likely to do nothing to pursue vaccination. The most frequent reason for inaction was being married or in a monogamous relationship, but other reasons relating to uncertainty about the vaccine and insurance/cost issues were common.
These reasons for inaction echo findings of previous studies, which noted a perceived lack of need, concerns about the vaccine, and perceived barriers as factors in the decision not to be vaccinated. A perceived lack of need, usually due to sexual inactivity or low risk, was found to be a factor in previous population surveys of this age group [
14,
15]. Safety of the vaccine was also raised as an issue in these surveys [
14,
15]. In a study of college-age women, those who had decided to forego vaccination were less sure of the vaccine's safety and were less knowledgeable about risk factors, transmission, and methods of detection of HPV than were women who had been vaccinated [
19].
As in the present study, a relatively small proportion of women (7%) in the National Immunization Survey (NIS) 2007 were concerned about cost or insurance issues [
15]. Cost was also a barrier reported by college women who had chosen not to receive the vaccine [
19]. However, larger numbers reported other barriers to vaccination, including lack of time or failure to make a doctor's appointment (21% in the NIS 2007) [
15]. Similarly, in a follow-up study that included women aged 13-26, 45% of young women who had not yet been vaccinated had simply not returned to the clinic in the six months since the baseline study [
13].
In our previous paper published from this data set we found that those respondents who reported physician discussion/recommendation of HPV vaccination were significantly more likely to be in the vaccinated group [
17]. The women described here remained unvaccinated, and only 30.1% had received a recommendation from their physician to be vaccinated, with only 15% receiving a strong recommendation.
Responses to questions about taking additional action suggested ambivalence on the part of non-vaccinees (almost 70% were at least somewhat likely to ask a doctor to get the vaccine, while 48% expressed being at least somewhat likely to do nothing). This inconsistency may have resulted from the choice of cutoff ("somewhat," "very," and "extremely" likely) in the accepted responses. There was no discrepancy if the threshold was set at "very" or "extremely" likely, when from 27.8% to 50.0% would take some action regarding the vaccine, and 27.1% would do nothing. Ambivalence about vaccination is, however, consistent with the lack of correlation between the intention to be vaccinated and actual vaccination observed in one post-vaccine study [
13]. This result may explain the discordance in the United States between the findings of studies carried out before the vaccine became available, which showed favorable attitudes toward HPV vaccination (74-89% acceptance rate) [
20-
23], and current low vaccination rates (5-36%) [
12,
13]. Alternatively, these low rates of vaccination may reflect an inefficient method of vaccine delivery for young adult women in the United States. In countries with school-based vaccination programs for girls, there is good agreement between rates of pre-vaccine acceptance and actual vaccination. In England, for instance, more than 80% of people surveyed were in favor of HPV vaccination [
24], and school-based programs have reported more than 70% uptake of the first vaccine dose among 12-13 year-olds [
25,
26]. In Australia, the pre-vaccine acceptance rate was about 80% [
27]. When a school-based program in Queensland contracted with a general practice to provide recommended immunizations, uptake of all three doses of the HPV vaccine was 79% [
28].