Figure 3.

Omicron breakthrough infection specifically increases neutralization activity against Omicron

(A) Schematic representation of plasma samples collected from individuals previously infected or not, who received 3 doses of mRNA vaccine and were affected or not by Omicron breakthrough infection were tested for neutralization activity against pseudo viruses expressing the WH1, B.1.217.2 (Delta), BA.1, BA.2, and BA.4/5 SARS-CoV-2 Spike proteins. Plasma samples were collected at about 1 month after last vaccination or 1 month after breakthrough infection if the latter happened.

(B) Raw ID₅₀ (reciprocal dilutions) titers against the indicated variant Spikes. Horizontal bars and numbers indicate ID₅₀ geometric means (GMT) for each group and error bars indicate 95% confidence intervals. At the bottom are fold changes for the indicated comparisons. Significant p values are indicated for comparisons between all groups (Kruskal-Wallis test with two-stage step-up multiple comparison, ∗p < 0.05). Dashed lines indicate the assay lower limit of detection (60 reciprocal dilutions). Responder rates were all 100% (ID₅₀ > 60). Participants (3 of the +/3/− group and 2 of the +/3/+ group) who only received 1 dose as part of the full vaccine schedule are indicated in blue.

(C) Ratio of WH1 ID₅₀ over the indicated VOC ID₅₀ calculated for the groups with plasma samples at 1 month (shown in 3A) after last event (infection or vaccination). Horizontal bars indicate ratio geometric means for each group and error bars indicate 95% confidence intervals. Bottom numbers indicate fold reduction compared to WH1. Significant p values are indicated for comparisons between all groups (Kruskal-Wallis test with two-stage step-up multiple comparison, ∗p < 0.05, ∗∗p < 0.01). Participants (3 of the +/3/− group and 2 of the +/3/+ group) who only received 1 dose as part of the full vaccine schedule are indicated in blue. See also Figures S5 and S6.