Methods Study design
A phase II randomised, multicentre, double-blind placebo-controlled study of a quadrivalent HPV (type 6, 11, 16, and 18) L1 VLP vaccine was done in two parts. Part A was a sequential dose-escalation safety assessment, in which participants, investigators, and staff were blinded as to assignment of vaccine or placebo, but not to assignment of doses in the active-treatment group. Part B was a fully blinded dose-ranging assessment of immunogenicity and efficacy. Study procedures for individuals in part A and part B were identical. The results presented in this article are from part B.
1158 women aged 16-23 years were recruited in Brazil, Europe, and the USA. The study enrolled healthy women, who were not pregnant, had no previous abnormal Pap smears, and reported a lifetime history of four or fewer male sex partners. Enrolment of virgins was restricted to women who were 18 years or older and who were seeking contraception. This study did not exclude women with previous HPV infection. Participants were required to use effective contraception during the trial.
The active quadrivalent vaccine was a mixture of four recombinant HPV
type-specific VLPs (Merck Research Laboratories, West Point, PA, USA) consisting of the L1 major capsid proteins of HPV 6, 11, 16, and 18 synthesised in Saccharomyces cerevisiae.10,14,16 The four VLP types were purified and adsorbed onto amorphous aluminium hydroxyphosphate sulfate adjuvant. The placebo consisted of the same adjuvant and was visually indistinguishable from vaccine.
Three preparations of a quadrivalent HPV types 6, 11, 16, and 18 L1 VLP were used. The three preparations were : 20 É g type 6, 40 É g type 11, 40 É g type 16, and 20 É g type 18, with 225 É g aluminium adjuvant ; 40 É g type 6, 40 É g type 11, 40 É g type 16, and 40 É g type 18, with 225 É g aluminium adjuvant ; and 80 É g type 6, 80 É g type 11, 40 É g type 16, and 80 É g type 18, with 395 É g aluminium adjuvant. The study had two placebo groups with adjuvant doses of 225 É g or 450 É g for appropriate safety comparisons.
0·5 mL vaccine or placebo was given by intramuscular injection at day 1,
month 2, and month 6. After vaccination, participants were observed for 30 min. Temperatures were also recorded orally every day in the evening for 5 days after vaccination, and the participant noted adverse events by standard diary card for 14 days after vaccination.
Gynaecological examination was done at day 1 and at months 7, 12, 24, and 36. A ThinPrep Pap test (Cytyc, Boxborough, MA, USA) and external genital,
lateral vaginal, and cervical swabs for PCR analysis of HPV were obtained from all participants at day 1 and at months 7, 12, 18, 24, 30, and 36. Biopsy samples of external genital lesions identified during the study were taken, and serum samples were obtained at day 1 and months 2, 3, 6, 7, 12, 18, 24, 30, and 36.
This study was done in accordance with national or local requirements for
ethics-committee review, informed consent, and other statutes or regulations regarding the protection of the rights and welfare of those participating in biomedical research. All individuals, or their parents or legal guardians, gave written informed consent after review of the protocol procedures.
The aim of the study was to assess a quadrivalent HPV L1 VLP vaccine in terms of the composite primary endpoint of persistent infection associated with HPV 6, 11, 16, or 18, or cervical or external genital disease compared with placebo. Women with persistent infection were defined as those who had the same vaccine-HPV-type DNA in cervicovaginal samples obtained 7 months after vaccination as those obtained from two or more consecutive visits (required to be 4 months or longer apart unless at least one tissue sample was diagnosed as cervical disease by a panel of pathologists), or as those who had vaccine-HPV-type DNA detected in a sample recorded during the last visit before being lost to follow-up. HPV-associated disease was defined as a tissue sample diagnosed as CIN by a panel of pathologists 7 months after vaccination ; vulval intraepithelial neoplasia ; vaginal intraepithelial neoplasia ; external genital warts ; or cervical, vulval, or vaginal cancer with vaccine-HPV-type DNA detected in tissue from, or in a swab of, the same lesion and in cervicovaginal samples obtained at the visit before the biopsy visit.