New findings demonstrate a recent increase in the annual completion rates of vaccination against human papillomavirus (HPV) infection, which is a necessary cause of cervical cancer. However, the data, from a large and nationally representative sample of female adolescents, also show that significant gaps persist in vaccination completion according to race/ethnicity and poverty.
Linda M. Niccolai, PhD, with the Yale School of Public Health in New Haven, Connecticut, and associates used data obtained in the 2008 and 2009 National Immunization Survey on teenage girls (NIS-Teen) who received at least 1 dose of HPV vaccine.
Two HPV vaccines are approved by the FDA to protect against HPV-16 and HPV-18, which are responsible for 70% of cervical cancer cases. The Advisory Committee on Immunization Practices (ACIP) recommends the routine use of either vaccine in a 3-dose series for girls aged 11 or 12 years. The second and third doses should be given at 2 and 6 months, respectively. A catch-up vaccination is also recommended up to age 26 for girls and women who did not previously receive all 3 doses.
Several studies have documented suboptimal HPV vaccination completion rates ranging from 13% to 16%. White adolescents have been found to be more likely to complete the series than Hispanics and blacks, and teens with private insurance were more likely to complete the series than teens with public insurance.
However, prior studies showing disparities in HPV vaccination completion have been plagued by limitations. For example, the earlier investigations did not directly examine completion rates using multivariate modeling to assess independent correlates of completion. They have also been limited by small "and possibly nonrepresentative samples."
The primary outcome measure in the present study was completion of the 3-dose series defined as having received at least 3 doses of either vaccine as documented in healthcare provider reports.
Overall, 55% of girls who had initiated HPV vaccination completed the 3-dose series, 21% received 1 dose, and 24% received 2 doses.
The percentage that completed the series was significantly higher in 2009 than 2008 (60% vs 48%; P <.001).
After adjusting for covariates, including access to care, adolescents who were black (adjusted odds ratio [AOR] = 0.48; 95% confidence interval [CI] = 0.40-0.57) or Hispanic (AOR = 0.75; 95% CI = 0.64- 0.88) were significantly less likely to complete the vaccination series than whites. Adolescents living below the federal poverty level were significantly less likely to complete vaccination than adolescents with household incomes > $75,000 (AOR = 0.76; 95% CI = 0.63-0.92).
The interaction between race/ethnicity and year was not significant (P = 0.92).
Niccolai et al described the hike in HPV vaccination completion rates from 2008 to 2009 as "far from optimal" but "encouraging." Completion of the vaccination series may be problematic because the first dose may be administered at a routine yearly preventive appointment, but the second and third doses require follow-up visits. These subsequent appointments, in turn, call for "knowledge, motivation, positive attitudes toward vaccination, and additional financial resources such as the ability to pay for vaccine or, if the cost of vaccine is covered by health insurance or a government program, the ability to take time off work for parents, transportation visits, or office visit copayments."
The authors caution that the precise extent to which the study cohort is representative of all adolescents living in the United States is not known despite a "strong survey design and use of weights." A major reason is that the study lacked potentially important information on doses of HPV vaccine given by providers other than those who responded to the provider survey. In addition, the study was not able to determine whether adolescents who had not completed the vaccination series had not done so because they had only begun the series within the prior 6 months.
Also, the NIS-Teen survey did not include other factors that might be relevant, including the employment status of the parents and family structure.