Infection with human papillomavirus (HPV) is a serious public health concern with significant morbidity and financial consequences. The most prevalent strains of HPV, subtypes 16 and 18, are leading causes of cervical and anal cancers nationally.^1,2 Cervical cancers caused by persistent HPV infections have led to an estimated 8.1 deaths per 100,000 women nationally and 8.3, 6.4, and 11 deaths per 100,000 for whites, African Americans, and Latinos, respectively, in California.³ The prevalence of HPV is highest (45%) among young women aged 20 to 24 years,^4,5 and the likelihood of HPV infection is about 75% among adults aged 15 to 49 years.² The costs of treating HPV and its related disease are estimated at or above $4 billion annually.⁶

Two HPV vaccines, Gardasil and Cervarix, became available in 2006 and 2009, respectively.^7,8 Gardasil guards against subtypes 6, 11, 16, and 18; Cervarix guards against subtypes 16 and 18 only. Both are nearly 100% effective against precancerous lesions, with Cervarix more effective against persistent infections (nearly 100%) than Gardasil (86-89%).^1,2 The vaccines are recommended for young females aged 12 to 26 years and may have some benefits for older women.^9-11 Financial constraints may be a significant barrier to HPV vaccination. The vaccine, at an estimated cost of $360 for the 3-dose vaccine plus the associated administration and visit fees (estimated at $92), is too expensive without insurance coverage for most low-income families.¹²

Free vaccine for children may be obtained from various sources including the federally funded Vaccine for Children (VFC) program, which covers about 40% of poor children²; and the Immunization Grant Program (Section 317), which is subject to budget shortfalls.² Vaccine manufacturers may cover uninsured adults and Medicaid may cover vaccine costs for adults.⁴ The scope of these forms of coverage is unknown and the underinsured may still have limited access.¹³

Among privately insured patients, the vaccine may not be covered or covered fully.¹⁴ In early 2008, some preferred provider organizations (PPOs) in California did not cover the vaccine.¹² Lack of coverage or knowledge of coverage for the vaccine is a frequently reported reason for not vaccinating against HPV.¹⁵ Differential rates of compliance with the federal Advisory Committee on Immunization Practices by PPOs versus health maintenance organizations (HMOs) shortly after availability of the HPV vaccine, as well as higher cost-sharing requirements by PPOs, may have led to additional barriers to vaccination according to the type of private insurance coverage. Overall, high costs and inadequate coverage of the HPV vaccine are likely to lead to uneven vaccination rates among lowincome and other disadvantaged groups. Understanding the impact of financial barriers on adherence to HPV vaccination is needed to improve HPV vaccination rates and to prevent HPV infection and its disease sequelae among all eligible-age females.¹⁶

METHODS

Data and Sample

We used the 2007 California Health Interview Survey (CHIS) for this study. The survey is a representative randomdial telephone survey of more than 53,600 households, including about 51,000 adults, and is conducted in English, Spanish, Mandarin, Cantonese, Korean, and Vietnamese languages to capture the great majority of non–English speaking populations. It has an overall response rate of 21.2% and has been found in multiple studies to be representative of the California population.¹⁷ The sample included all females aged 18 to 26 years (n = 1840) as well as girls aged 8 to 17 years (n = 5765) who are recommended to receive HPV vaccination. Parents of teenagers answered the CHIS vaccination questions to increase the reliability of responses and because the vaccination decision is most likely to be made by parents of minors.

Conceptual Framework, Research Questions, and Hypotheses

We used Andersen and Davidson’s conceptual framework for healthcare use.¹⁸ Based on this conceptual framework, HPV vaccination or intent to vaccinate was determined by enabling factors (insurance, income, and affordability of care), predisposing factors (eg, age, race), and need (eg, health status). Our primary interest was to assess the impact of enabling factors. Specifically, we wanted to determine how insurance, income, and affordability of care affect HPV vaccination rates and patients’ willingness to pay.

We hypothesized that rates of HPV vaccination or intent to vaccinate and willingness to pay for the vaccination are lower for individuals without insurance coverage or with PPO or fee-for-service (FFS) coverage, for some low-income populations (as measured by federal poverty level [FPL]), and for individuals who reported that care has been unaffordable (as measured by having delayed or forgone needed healthcare due to cost/no insurance in the past year). We assumed that some eligible individuals fell through the gaps despite availability of VFC and other programs. We also examined the role of enabling factors in knowledge of the HPV vaccine, hypothesizing that vaccine knowledge was lower among lower income and uninsured groups who were not targeted by vaccine manufacturers’ advertising campaigns early on.

Dependent Variables

Five different dependent variables are included in this study. Adults and parents (Figure) were asked (1) if they had heard of the HPV vaccine prior to the survey. Those who had heard of the vaccine were asked (2) if they/their daughters had received at least 1 dose of the HPV vaccine, and if so (3) whether they/their daughters had received all 3 doses. Respondents who had not heard of the vaccine were informed of the existence and intent of the vaccine and were then asked (4) if they were interested in receiving the vaccine (adults) or giving it to their daughter if a doctor recommended it. Those who were interested in receiving the vaccine were asked (5) if they were willing to pay $360 for the 3-dose vaccine.

Independent Variables