Breakthrough infections with SARS-CoV-2 omicron efficiently boost antibodies from previous BNT162b2 vaccinations

OBJECTIVE: To investigate whether SARS-CoV-2 omicron breakthrough infection in individuals after three doses of wildtype-based BNT162b2 increases antibody levels measured by a commercially available wildtype-based immunoassay. METHODS: 16 of 21 individuals in a BNT162b2 vaccination cohort (recruited 129 [129–135] days after dose 3) experienced a breakthrough infection (BTI) between March and September 2022. Antibodies to the receptor binding domain (RBP) of the spike protein (Anti-S) were quantified using the wildtype-based Elecsys SARS-CoV-2 S assay (Roche). Antibody responses of triple vaccinated BTI cases were compared to triple vaccinated individuals without breakthrough infection and to 16 matched individuals after primary omicron infection. RESULTS: In the 16 individuals with primary Omicron infection, the anti-S assay returned only very low results (2.25 [0.61–5.80] U/mL). However, in individuals with BTI, Anti-S levels rose from 7,135 [5,870–17,470] U/mL to 21,705 (7,750–46,137.5) U/mL. At the same time, Anti-S concentrations decreased from 9,120 [7,480–13,480] U/mL to 3,830 (2,390–4,220) U/mL in those 5 of 21 vaccinated only. CONCLUSIONS: Our data suggest that breakthrough infection with omicron can efficiently boost wild-type antibodies in individuals vaccinated with wild-type BNT162b2.