Methods: ZV was administered to participants ≥70-year old as a second dose (G1; N=201) to subjects who had received ZV ≥10 years previously and as a first dose to age-matched controls (G2; N=199). CMI was measured by dual-color IL2 and IFNγ FluoroSPOT. The same assay control was used during the entire study to ensure consistency of the results.
Results: At 3 years after ZV administration, 156 of 201 G1 and 137 of 199 G2 participants contributed to analysis. The number of VZV-specific IFNγ+IL2+/- effector, IFNγ +/-IL2+ memory and IFNγ+IL2+ effector-memory spot forming cells (SFC) did not differ between entry and 3 years in either group (p≥0.45). The SFC comparison between the two groups showed similar IFNγ+IL2+/- and IFNγ+/-IL2+ SFC at 3 years (P≥0.14) and a trend towards higher IFNγ+IL2+ SFC in G1 vs. G2 (p=0.07).
VZV CMI in adults ≥70-year 3 years after a second (booster) dose of ZV was similar to the baseline. At 3 years, the boosted group maintained only a marginal advantage in IFNγ+IL2+ effector-memory T cells and had similar IFNγ+/-IL2+ total memory and IFNγ+IL2+/- total effector T cells compared with the first-time immunized group. The clinical significance of these findings remains to be determined.
K. Schmader, Merck: Investigator , Research support
M. Johnson, Merck: Investigator , Research support
Y. Caldas, Merck: Investigator , Research support
J. Canniff, Merck: Investigator , Research support
A. Cho, Merck: Investigator , Research support
B. Mccarson, Merck: Employee , Salary
J. Martin, Merck: Employee , Salary
Z. Popmihajlov, Merck: Employee , Salary