Abstract
BACKGROUND: Affordable HPV vaccines are needed to accelerate elimination of cervical cancer. We evaluated the efficacy, safety, and immunogenicity of a recombinant bivalent human papillomavirus (HPV) vaccine composed of L1 virus-like particles (VLPs) for HPV 16 and HPV18 (HPV-2), produced in Pichia pastoris, in healthy Chinese women aged 18-30 years. METHODS: In this phase 3, double-blind, randomised, placebo-controlled trial conducted at 10 centres in China (Nov 2014-Jan 2020), participants were assigned 1:1 to receive three doses of HPV-2 or placebo at months 0, 2, and 6. The primary endpoint was efficacy against histopathology-confirmed cervical intraepithelial neoplasia grade 2 or higher (CIN2+) associated with HPV16/18 through 48 months. Secondary endpoints were safety (adverse events [AEs] within 1 month of any dose; serious AEs throughout follow-up) and immunogenicity (neutralising antibody titres and seroconversion at Month 7 in a predefined subset). RESULTS: Of 12,000 women enrolled, 11,999 received the first dose and 11,281 completed all three doses. Over 48 months, 17 CIN2 + cases occurred: 3 among vaccine recipients (n = 5190) versus 14 among placebo recipients (n = 5167), corresponding to vaccine efficacy of 78.6% (95% CI 23.3-96.1; p = 0.012). No vaccine-related serious AEs occurred. Solicited local AEs were mainly mild pain, reported by 25.9% of vaccinees and 7.9% of placebo recipients. Fever was the most common systemic AE (27.4% vs. 26.4%). In the immunogenicity subset, 99.7% (349/350) and 99.4% (348/350) of vaccinees were seropositive for HPV16 and HPV18 neutralising antibodies, respectively, at Month 7. CONCLUSIONS: Three doses of HPV-2 were well tolerated, highly immunogenic, and efficacious against CIN2 + up to 4 years post-vaccination, supporting further evaluation in the adolescent target population for HPV vaccination campaigns. TRIAL REGISTRATION: China Drug Trials Registry (CTR20140626; registered Sept 26, 2014; prospective). CLINICALTRIALS: gov (NCT02733068; registered April 11, 2016; secondary).