Memory B-cells elicited by different HPV vaccine regimens in the DoRIS randomised controlled trial

Prophylactic human papillomavirus vaccines such as Cervarix® and Gardasil®9 induce robust and sustained antibody responses over time. One driver of such responses is memory B-cells (MBCs), primed during initial HPV-vaccine exposure. As part of the Dose Reduction Immunobridging and Safety Study (DoRIS), MBCs were evaluated in peripheral blood mononuclear cells by enzyme-linked immunosorbent spot assay at baseline and at 5 visits post-first vaccine dose to Month 36 in 930 Tanzanian girls randomly allocated to 3, 2, or 1 doses of either vaccine. Most ( > 90%) participants had detectable MBCs at all time points, with maximum responses by Month 7. Geometric mean frequency HPV-specific MBCs and the proportion responding declined thereafter for both vaccines in the 2 and 3-dose arms. MBC frequencies were lower in single-dose than in 2- and 3-doses recipients at all time points subsequent to Month 1. By Month 36, MBC responses to both vaccines for both HPV16 and 18 were similar across all dosing arms. The clinical significance of the dose response remains to be evaluated; however, the presence of MBCs in the circulation after 3 years with a single vaccine dose is encouraging in terms of generating long-lasting protection with a one-dose vaccination strategy.