Figure 3.

Neutralizing antibody titres at N_300 (after a median of 291 days from diagnosis in unvaccinated HCWs), corresponding to V0 in vaccinated HCWs and at N_390 (after a median of 394 days from diagnosis), corresponding to the last time point of vaccinated HCWs (V2_90: 90±2 days after the second dose).

Data are reported as individual ID₅₀ values and as median value at each study time.

The same symbols indicate the same HCWs at different time points.

ID₅₀: reciprocal value of the sample dilution that showed a 50% protection of virus cytopathic effect

V0: before receiving the first dose

V2_90: 90±2 days after the second dose

N_300: after a median of 291 days from diagnosis

N_390: after a median of 394 days from diagnosis