After the World Health Organization (WHO) designated the omicron variant of concern (VOC) on the 26 November 2021, the extremely rapid spread of this variant is replacing the delta VOC with increased risk of vaccine-breakthrough infection in the South Africa, in European countries and in the United States.1 Both vaccine-induced neutralising antibodies (NAbs) and current NAbs in combination therapy have shown significantly reduced activities.2,3 Till now, it remains unclear whether vaccine-induced memory responses can be recalled by the omicron viral infection. These results demonstrated that although the omicron VOC evaded BNT162b2 vaccine-induced NAbs, the breakthrough infection could recall cross-reactive bNAbs generally against all current VOCs in both OP1 and OP2. Vaccine-breakthrough infection by the SARS-CoV-2 omicron variant elicits broadly cross-reactive immune responses. [Extracted from the article]