Figure 3.

Neutralizing antibody (Nab) responses against infective SARS-CoV-2. Panels (A–C) refer to samples tested from volunteers immunized with the prime–boost protocol for ChAdOx1 nCoV-19 on days 0 and 90 (indicated by arrows). Individual serum samples were collected before vaccination (0 days = pre-immunization) to determine a baseline profile. In addition, volunteer samples were collected on days 7, 15, 30, and 90 post-first dose and 30 days after the second immunizing dose; this point is represented on the graphs as day 120. Panels (A–C) belong to volunteer groups including individuals without (noCOVID-19) or with (COVID-19) pre-vaccination SARS-CoV-2 infection and the comparison of these two groups. Sera were serially diluted from 1:10 to 1:31,250 and the PRNT50% was performed in 24-well plates. Asterisks indicate differences that are statistically significant (* p < 0.05, ** p < 0.01, and *** p < 0.001) as evaluated by Kruskal–Wallis tests with Dunn’s post-hoc tests (A,B) and Mann–Whitney tests (C). DAV = days after vaccination.