FASTER-Tlalpan Study in Mexico: HPV Vaccination Impact on Cervical Cancer Screening Program

Cervical cancer mortality is a reflection of social inequity in health care. Globally, 266,000 women die from cervical cancer annually, and 85% of these deaths occur in low- and middle income countries (LMIC).1,2 Persistent infection with high-risk human papillomavirus (hrHPV) is a necessary cause of cervical cancer.3,4 HPV16 and HPV18 are responsible for 70% of squamous cell carcinomas, and in conjunction with HPV45, cause 94.2% of cervical adenocarcinomas.4 The introduction of HPV vaccines will change the epidemiology of HPV-related cancers. However, it may take 30 years to observe the desired benefits of widespread vaccination when vaccinated cohorts reach the peak ages at which cervical cancer cases currently occur (e.g. women aged 40-50 years).5 As of August 2015, 84 countries and territories had national public-sector HPV immunization programs and 38 had pilot programs.6 These programs mainly target adolescent girls to obtain the greatest cost-benefit ratio,7 considering the initial price of the vaccine (>$100 US per dose).8,9 Women older than age 25 are also vulnerable to new HPV infections10 and could also be vaccinated depending on country-specific resource availability.

Recent results of Phase III HPV vaccination trials documented that the vaccine's efficacy among adult women is excellent (efficacy >80% to prevent resultant HPV-related cervical intraepithelial neoplasia).11,12 Additionally, current vaccines protect against both HPV16 and HPV18 as well as provide cross-protection against other HPV types, particularly types 31 and 45.13 Broad-spectrum protection such as this may lower the need for subsequent screening, warrant longer screening intervals than those currently used, and offer novel prevention policies against HPV-related cancers. The combination of vaccination and screening strategies to prevent cervical cancer may be particularly appropriate in countries with high incidence of cervical cancer that have already implemented hrHPV-based screening programs. These criteria are satisfied in Mexico.14 A broader age range of females in population-based HPV vaccination programs could have direct benefits for vaccinated females, and indirect benefits for non-vaccinated females and male sexual partners via increased herd immunity to reduce HPV-related cancers.15 Based on the high efficacy of the HPV vaccine in older women, a novel strategy combining vaccination and screening, HPV FASTER, has been proposed.16 In accordance with this proposal, HPV vaccination of women in a broad age range can offer protection to women who are not currently infected, but also can protect against subsequent re-infection.16 As a result, a combined strategy of HPV vaccination and screening may reduce the lifetime number of screens used by the current hrHPV-based screening programs. If a screening and vaccination strategy is widely adopted, we expect promising results. This strategy has the potential to: 1) mitigate the screening demand on both women and health services by extending screening intervals; 2) improve the cost-benefit balance of screening programs; and 3) provide greater protection and quality of life to a large number of women through a reduction in cervical cancer.17 An intervention such as this may not only save many lives in the next 30 years but also be cost-effective.

However, the data on efficacy of HPV vaccination in older women to reduce cervical cancer risk, and not just the risk of precancerous lesions, are lacking. That is, there is currently insufficient knowledge regarding the role of HPV vaccination in older women to permit screening intervals to be extend safely following a negative screen (Figure 1).

A significant challenge for HPV-vaccine uptake is the number of doses in the standard vaccine schedule. Although licensed in some countries for use among older individuals, national HPV vaccination programs target teenagers and young adults. Recent studies found that fewer than three doses of the two commercially available prophylactic HPV vaccines seem to provide similar protection against cervical HPV16 and HPV18 infections as the three-dose schedule in women younger than 25 years old. 18,19 Herein we propose a population-based study to assess the efficacy of a 2-dose HPV vaccination with [HPV16/18 AS04-adjuvanted vaccine (Cervarix ®) and HPV 6/11/16/18 vaccine (Gardasil®)] against HPV-persistent infection and HPV-related cervical disease in older women between 25 and 45 years of age attending clinics for hrHPV-based screening.