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CDC Fact Sheet: Differences
between Advisory Committee on Immunization Practices (ACIP) and American
Cancer Society (ACS) HPV vaccine recommendations |
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February 7, 2007 ACS and ACIP recommendations are similar. Both recommend vaccination targeting 11 to 12 year-old females. The ACS recommendations differ from ACIP in that ACS recommends catch-up vaccination of 13 to 18 year-old females; ACIP recommends catch-up vaccination of 13 to 26 year-old females. The ACS recommendation states that there are insufficient data to recommend vaccination of 19 to 26 year-olds. The reasons provided include that the clinical trials were done in 16 to26 year-old women who had less than five sexual partners (median, two partners) and that there are no cost effectiveness data for this age group. The background information reviewed by ACIP to develop recommendations included data from the vaccine trials, natural history studies of HPV, national studies on sexual behavior, and data from economic analyses. ACS guidelines primarily focus on cancer prevention, while CDC guidelines include consideration of other outcomes, including genital warts. Females 19 to 26 years of age who are not yet sexually active can be expected to have the full benefit of vaccination. Although sexually active females in this age group might have been infected with one or more vaccine HPV types, type-specific prevalence studies in the United States suggest that only a small percentage of sexually active females in this age group have been infected with all four of the HPV vaccine types. These data, available from North American participants 16 to 24 years of age in the quadrivalent HPV vaccine trials, showed that 24% had evidence of exposure to one of the 4 HPV vaccine types, but less than 1% had evidence of exposure to all four types. Among females with four lifetime sexual partners, only 4% had evidence of current or past exposure to all four types. Even assuming that laboratory methods may have underestimated exposure, the percentage of females exposed to all four types would be quite small. Of note, females in the vaccine trial population were more likely to have ever had sex than similar-aged females in the general United States population. Among those sexually active, the median number of lifetime sexual partners, two, was similar in trial participants and females in the general United States population. At a clinical level, it is not possible for a provider to determine which women already have been exposed to HPV vaccine types. There is no clinically available serologic test to determine exposure. The commercially available Digene Hybrid CaptureŽ 2 (HC 2) tests for current infection with a group of high risk types and does not identify specific HPV types. As demonstrated by the HPV vaccine clinical trials, the quadrivalent HPV vaccine does not appear to protect against persistent infection, cervical cancer precursor lesions, or genital warts due to an HPV type that females are infected with at the time of vaccination. However, females in the trials who were already infected with one or more vaccine HPV types prior to vaccination were protected against disease caused by the other vaccine HPV types. Therefore, while overall vaccine effectiveness would be lower when administered to a population of females who are sexually active, and would decrease with older age and likelihood of HPV exposure with increasing number of sex partners, most females in this age group will derive at least partial benefit from vaccination. According to the most comprehensive HPV model published to date, and the only model currently available that looks at the impact of vaccination against all four HPV types included in the quadrivalent vaccine, the inclusion of 19 to 26 year-olds in the catch-up vaccination can be considered cost-effective compared to many other public health programs. Specifically, expanding the vaccination to include those aged 19 to 26 years can prevent thousands of cases of cervical cancer over the next 25 years at an estimated cost of about $10,000 per quality-adjusted life year gained.
Sources: Elbasha EH, Dasbach EJ, Insinga RP. Projecting the epidemiologic and economic consequences of a quadrivalent HPV vaccine in the United States. ACIP meeting presentation, October 2006, Atlanta GA. http://www.cdc.gov/nip/acip/slides/oct06/08_HPV_Vaccine/hpv-3-elbasha.pdf |