Persistence of the Immune Response to an Intramuscular Bivalent (GI.1/GII.4) Norovirus Vaccine in Adults

Major global economic and health burdens due to norovirus gastroenteritis could be addressed by an effective vaccine. In this study, 428 adult recipients of various compositions of the norovirus vaccine candidate, HIL-214, were followed for 5 years, to assess immune responses to its virus-like particle antigens, GI.1 and GII.4c. Serum antibodies and peripheral-blood antibody-secreting cells (ASCs) were measured. This report focuses on the single-dose 15/50 (µg GI.1/GII.4c) composition, which had been selected for further clinical development. For single-dose 15/50 recipients (N = 105), GI.1-specific and GII.4c-specific histoblood-group antigen-blocking (HBGA) antibodies appeared to have persisted to 5 years, waning from a peak at 4 to 8 weeks, and plateauing above baseline after 3 years. From 3 to 5 years, GI.1-specific GMTs ranged between 53 (95%CI, 40-71) and 60 (95%CI, 46-77; N = 69-97) and were approximately 2-fold above the baseline GMT (24 (95%CI, 20-28); N = 105). GII.4c-specific GMTs ranged between 103 (95%CI, 77-138) and 114 (95%CI, 86-152; N = 70-97) and were above baseline, but by less than 2-fold (70 (95%CI, 53-92); N = 105). Similar kinetics were observed for pan-Ig titers and ASCs in a subset. Similar kinetics were also observed for HBGA and pan-Ig titers in recipients of other 15/50 dosages. Immune responses to HIL-214 in adults appear to persist for five years.