Memory Cell and Antibody Responses Following a Single Versus Two Doses of Escherichia coli-Produced Vaccine Against Human Papillomavirus Types 16 and 18: A Real-World Study in Chinese Girls.

A comprehensive profile of immunogenicity induced by a single dose of human papillomavirus (HPV) vaccination has yet to be presented. We report interim data from an ongoing non-interventional real-world study comparing the memory cell and antibody responses following single- and two-dose regimens of the Escherichia coli-produced HPV-16/18 vaccine in Chinese girls aged 9-14 years. HPV-16/18-specific neutralizing antibodies, IgG antibodies, and memory B- and T-cell responses were assessed and compared between the single-dose and two-dose groups. The results showed that among 492 per-protocol participants (298 two-dose; 194 single-dose), the median time from Dose 1 to blood sampling was 12.07 months. Single-dose neutralizing antibody seropositivity exceeded 90% for HPV-16 and approached 80% for HPV-18. The antibody avidity index of HPV-16 IgG after a single dose was non-inferior to that after two doses (lower bound of the geometric mean avidity ratio > 0.5). Both dosing schedules induced HPV-16/18-specific memory B- and T-cell responses with similar positivity and geometric means (p > 0.05). Therefore, a single dose of the E. coli-produced HPV-16/18 vaccine elicited robust antibody quantity and quality, with memory B- and T-cell responses comparable to those induced by two doses, supporting its potential for population-level implementation and contribution to the WHO target of vaccinating 90% of girls.