Immunogenicity of the adjuvanted recombinant zoster vaccine: persistence and anamnestic response to additional doses administered 10 years after primary vaccination.

BACKGROUND The adjuvanted recombinant zoster vaccine (RZV) is highly immunogenic and efficacious in adults ≥50 years (Y) of age (YOA). We evaluated (1) long-term immunogenicity of an initial 2-dose RZV schedule by following-up adults vaccinated at ≥60 YOA and by modeling, and (2) immunogenicity of 2 additional doses administered 10Y post-initial vaccination. METHODS Persistence of humoral and cell-mediated immune (CMI) responses to 2 initial RZV doses was assessed through 10Y post-initial vaccination, and modeled through 20Y using a Piecewise, Power law and Fraser model. Immunogenicity and safety of 2 additional RZV doses were also evaluated (NCT02735915). RESULTS Seventy adults were enrolled. Ten years post-initial vaccination, humoral and CMI responses were ~6-fold and ~3.5-fold above pre-initial vaccination levels, respectively. Predicted immune persistence through 20Y post-initial vaccination was similar across the 3 models. Sixty-two participants (82.6±4.4 YOA) received at least 1 additional RZV dose. Strong anamnestic humoral and CMI responses were elicited by 1 additional dose, without further increases after a second additional dose. CONCLUSIONS Immune responses to an initial 2-dose RZV course persisted for many years in older adults. Strong anamnestic immune responses can be induced by additional dosing 10Y after the initial 2-dose course.