BACKGROUNDThe World Health Organization (WHO) urges global administration of at least one dose of the HPV vaccine, particularly for girls aged 9-14, to work towards the elimination of cervical cancer. However, data on the efficacy of a single dose of Cecolin®, a bivalent HPV vaccine, remain quite limited. Therefore, it is crucial to design studies investigating the protective effects of a single dose of Cecolin® in Chinese girls.METHODSThe randomized clinical trial began on February 23, 2023 (NCT06345885). 198 Chinese girls aged 9-14 received a single dose of Cecolin® or Gardasil®. Seroconversion rates and geometric mean titers (GMTs) for HPV16 and HPV18 were assessed at one and two months post-vaccination. Non-inferiority was declared if the lower limit of the 95 % confidence interval (CI) exceeded -5 %. Safety of vaccine was evaluated in all vaccinated participants.RESULTSAt one month post-vaccination, both the Cecolin® and Gardasil® groups achieved 100 % seroconversion for HPV16 antibodies. The seroconversion rates for HPV18 were 97.9 % (95 % CI: 92.5 %, 99.7 %) in the Cecolin® group and 95.6 % (95 % CI: 89.1 %, 98.8 %) in the Gardasil® group. The GMTs in the Cecolin® group were significantly higher than those in the Gardasil® group for both HPV types, with GMT ratios of 1.5 (1.1, 2.1) for HPV16 and 2.84 (2.0, 4.1) for HPV18. The seroconversion rates and GMT ratios one month after a single dose of Cecolin® were non-inferior to those of Gardasil®, with results remaining consistent at two months. The incidence of adverse events was similar between the two groups throughout the study, with no statistically significant differences.CONCLUSIONThe immunogenicity and safety of a single dose of Cecolin® in Chinese girls aged 9-14 years were comparable to those of Gardasil. These findings support the use of single-dose Cecolin® to enhance HPV vaccination coverage for cervical cancer prevention.