Results
A substantial waning of neutralizing antibodies was observed after 6 months (23.1‐fold decrease), especially considering the XBB.1.5 subvariant. The estimated T1/2 of neutralizing antibodies was 16.1 days (95% CI=10.2–38.4 days). Although most participants still present a robust cellular response after 6 months (i.e., 95%), a significant decrease was also observed compared to the peak response (0.41 versus 0.95 UI/L, p=0.0083).