Can a single dose of human papillomavirus (HPV) vaccine prevent cervical cancer? Early findings from an Indian study.

BACKGROUND: Human papillomavirus (HPV) vaccination is a major strategy for preventing cervical and other ano-genital cancers. Worldwide HPV vaccination introduction and coverage will be facilitated if a single dose of vaccine is as effective as two or three doses or demonstrates significant protective effect compared to 'no vaccination'. METHODS: In a multi-centre cluster randomized trial of two vs three doses of quadrivalent HPV vaccination (Gardasil™) in India, suspension of the vaccination due to events unrelated to the study led to per protocol and partial vaccination of unmarried 10-18 year old girls leading to four study groups, two by design and two by default. They were followed up for the primary outcomes of immunogenicity in terms of L1 genotype-specific binding antibody titres, neutralising antibody titres, and antibody avidity for the vaccine-targeted HPV types and HPV infections. Analysis was per actual number of vaccine doses received. This study is registered with ISRCTN, number ISRCTN98283094; and with ClinicalTrials.gov, number NCT00923702. FINDINGS: Of the 17,729 vaccinated girls, 4348 (25%) received three doses on days 1, 60, 180 or later, 4979 (28%) received two doses on days 1 and 180 or later, 3452 (19%) received two doses on days 1 and 60, and 4950 (28%) received one dose. One dose recipients demonstrated a robust and sustained immune response against HPV 16 and 18, albeit inferior to that of 3- or 2-doses and the antibody levels were stable over a 4 year period. The frequencies of cumulative incident and persistent HPV 16 and 18 infections up to 7 years of follow-up were similar and uniformly low in all the vaccinated study groups; the frequency of HPV 16 and 18 infections were significantly higher in unvaccinated age-matched control women than among vaccine recipients. The frequency of vaccine non-targeted HPV types was similar in the vaccinated groups but higher in the unvaccinated control women. CONCLUSION: Our results indicate that a single dose of quadrivalent HPV vaccine is immunogenic and provides lasting protection against HPV 16 and 18 infections similar to the three- and two-dose vaccine schedules, although the study suffer from some limitations. Data on long term protection beyond 7 years against HPV infection and cervical precancerous lesions are needed before policy guidelines regarding a single dose can be formulated and implemented. Significant and long-lasting protective effect of a single dose can be a strong argument to introduce one dose of the HPV vaccine in many low income countries where the current standard of care for cervical cancer prevention is 'no intervention'.

Cervical cancer: screening and therapeutic perspectives.

Cervical cancer is a major cause of mortality and premature death among women in their most productive years in low- and medium-resourced countries in Asia, Africa and Latin America, despite the fact that it is an eminently preventable cancer. While cytology screening programmes have resulted in a substantial reduction of cervical cancer mortality in developed countries, they have been shown to have a wide range of sensitivity in most routine settings including in developing countries. Although liquid-based cytology improves sample adequacy, claims on improved sensitivity remain controversial. Human papillomavirus testing is more sensitive than cytology, but whether this gain represents protection against future cervical cancer is not clear. Recently, in a randomized trial, the use of visual inspection with 4% acetic acid was shown to reduce cervical cancer incidence and mortality. Cryotherapy and large loop excision of the transformation zone are effective and safe treatment methods for cervical intraepithelial neoplasia. The clinical stage of cancer is the single most important prognostic factor and should be carefully evaluated in choosing optimal treatment between surgery and radiotherapy, with or without chemotherapy. At the public health level, health care infrastructure, affordability and capacity for initiating and sustaining vaccination and screening programmes are critical factors in cervical cancer control. On the other hand, an informed practitioner can utilize the multiple opportunities in routine primary care interactions for prevention, screening, early detection and prompt referral for treatment.