Highlights•S IgG increased 6.6-fold after BA.1/2 infections and 3.6-fold after BA.4/5 infections.•N IgG increased 19.1-fold after BA.1/2 infections and 13.5-fold after BA.4/5 infections.•Sensitivity was 77.4% for the detection of post Omicron infection N IgG in vaccinated individuals.•The detection of S and N IgG increases in vaccinated populations remain sensitive.