Abstract
BACKGROUND: Prophylactic human papillomavirus (HPV) vaccination substantially alleviates cervical cancer burden. This study aimed to evaluate the safety, tolerability, and immunogenicity of an Escherichia coli-expressed recombinant nonavalent HPV vaccine. METHODS: A dose-escalating phase 1 clinical trial was conducted in Sheyang County, Jiangsu Province, China. Each participant received either the test vaccine or the control vaccine (Gardasil 9) following a 0/2/6-month schedule. Adverse reactions (ARs) within 7 days after vaccination, adverse events (AEs) within 30 days, and serious adverse events (SAEs) throughout the study were recorded. Blood parameters were measured before and 3 days after each dose. Serum immunoglobulin G (IgG) and neutralizing antibodies (nAbs) against nine HPV types were analyzed at months 0, 3, and 7. RESULTS: A total of 160 women aged 18-45 years were enrolled, and 155 participants completed the full vaccination regimen. Within 7 days following vaccination, the incidence of ARs ranged from 56.67% to 90.00%, with the low-dose group showing a significantly higher rate than the control group (p = 0.004). Most AEs were mild or moderate, and no vaccine-related SAEs occurred. No significant differences were observed among the four groups regarding the incidence of abnormal laboratory findings. Seroconversion rates for nAbs and IgG against nine HPV types exceeded 97.92% following three doses. High levels of nAbs and IgG were observed at months 3 and 7, with geometric mean titers (GMTs) showing further increases by month 7. CONCLUSIONS: This new recombinant nonavalent HPV vaccine exhibits good tolerability and strong immunogenicity among women aged 18-45 years, supporting further efficacy studies in larger populations.