Health and economic implications of HPV vaccination in the United States

Abstract

Background: The cost-effectiveness of prophylactic vaccination against human papillomavirus types 16 (HPV-16) and 18 (HPV-18) is an important consideration for guidelines for immunization in the United States.

Methods: We synthesized epidemiologic and demographic data using models of HPV-16 and HPV-18 transmission and cervical carcinogenesis to compare the health and economic outcomes of vaccinating preadolescent girls (at 12 years of age) and vaccinating older girls and women in catch-up programs (to 18, 21, or 26 years of age). We examined the health benefits of averting other HPV-16-related and HPV-18-related cancers, the prevention of HPV-6-related and HPV-11-related genital warts and juvenile-onset recurrent respiratory papillomatosis by means of the quadrivalent vaccine, the duration of immunity, and future screening practices.

Results: On the assumption that the vaccine provided lifelong immunity, the cost-effectiveness ratio of vaccination of 12-year-old girls was $43,600 per quality-adjusted life-year (QALY) gained, as compared with the current screening practice. Under baseline assumptions, the cost-effectiveness ratio for extending a temporary catch-up program for girls to 18 years of age was $97,300 per QALY; the cost of extending vaccination of girls and women to the age of 21 years was $120,400 per QALY, and the cost for extension to the age of 26 years was $152,700 per QALY. The results were sensitive to the duration of vaccine-induced immunity; if immunity waned after 10 years, the cost of vaccination of preadolescent girls exceeded $140,000 per QALY, and catch-up strategies were less cost-effective than screening alone. The cost-effectiveness ratios for vaccination strategies were more favorable if the benefits of averting other health conditions were included or if screening was delayed and performed at less frequent intervals and with more sensitive tests; they were less favorable if vaccinated girls were preferentially screened more frequently in adulthood.

Conclusions: The cost-effectiveness of HPV vaccination will depend on the duration of vaccine immunity and will be optimized by achieving high coverage in preadolescent girls, targeting initial catch-up efforts to women up to 18 or 21 years of age, and revising screening policies.

Figure 1. Vaccination Coverage

Pink boxes indicate vaccination of preadolescent 12-year-old girls at a coverage rate of 25% per year for the first 5 years of the vaccination program; purple boxes indicate a coverage rate of 75% in years 6 to 10 of the vaccination program. Without a catch-up program, each birth cohort of 12-year-olds had no future opportunities for vaccination beyond a single year. Yellow, light-orange, and dark-orange boxes indicate catch-up vaccination of girls and women from age 13 up to 18, 21, or 26 years of age, which occurred over a 5-year period at 25% coverage per year. Therefore, an additional 25% of the initial cohort of 12-year-old girls who were not vaccinated in the first year had another opportunity to receive the vaccine in the second year of the program, when they were 13 years old; such opportunities continued through program year 5. Brown boxes show catch-up vaccination in the initial cohort of 13-year-old girls. In year 1 of the vaccination program, 25% of the 13-year-old girls were assumed to be covered; in year 2, among the 75% of 13-year-olds who were not vaccinated in year 1, 25% would be covered when they were 14 years old. At the end of year 5, 76% of the original cohort of 13-year-olds was covered. The number of opportunities for vaccination depended on the specific catch-up strategy; for example, a 16-year-old in the first year of the program would have only three chances of receiving the vaccine in a catch-up program up to 18 years of age, since she would be older than 18 years of age in program year 4.

Figure 2. Effect of Inclusion of Other Health Conditions on the Cost-Effectiveness of Vaccination Strategies

The solid lines represent analyses in which the efficacy of the vaccine against human papillomavirus (HPV) was assumed to be 100% among girls and women without a previous history of type-specific infection (for all conditions). The dashed lines represent analyses in which the efficacy of the vaccine was assumed to be 50% (only for cancers other than cervical cancer and juvenile-onset recurrent respiratory papillomatosis [JORRP]; the efficacy remained 100% for cervical cancer and genital warts) among girls and women without a previous history of type-specific infection. In all analyses, the efficacy of the vaccine was assumed to be 0% among persons with a previous type-specific infection or infections. Including the potential benefits of the vaccine against noncervical HPV-16–related and HPV-18–related cancers, HPV-6–related and HPV-11–related JORRP, or both reduced the cost-effectiveness ratios, but the magnitude of the reduction depended on the specific outcomes included and the assumptions about efficacy. For instance, including other cancers reduced the cost-effectiveness ratios from 18% to 30% depending on the efficacy of the vaccine, whereas including JORRP had less of an effect. Under all assumptions, the cost of vaccination of preadolescent girls (i.e., 12-year-old girls) remained below $50,000 per quality-adjusted life-year (QALY), and the cost of catch-up vaccination of girls to 18 years of age was between $50,000 and $100,000 per QALY. The cost of catch-up vaccination of girls and women to 21 years of age decreased below $100,000 per QALY when other cancers or all outcomes were included, and the cost of catch-up vaccination to 26 years of age exceeded $100,000 per QALY, unless all outcomes were included with a vaccine efficacy of 100% for all conditions.