Recent publications in The Lancet Infectious Diseases have reported a marked decrease in neutralisation activity against the current SARS-CoV-2 omicron subvariants, such as XBB. 2.3 or BA. 2.86, when using serum samples or plasma from vaccinated individuals or those who have had a breakthrough infection. 1–4 More specifically, Keiya Uriu and colleagues3 suggested that the increased transmission potential of BA. 2.86 is related to its higher immune escape capacity. In our previous study, we have shown that high concentrations of salivary receptor-binding domain (RBD)-specific secretory IgA are associated with protection against breakthrough infection in individuals who have received mRNA-based vaccines. 5 Subsequent investigations showed that breakthrough infections caused by omicron might elicit a more potent, long-lasting, and cross-reactive mucosal immune response than vaccination alone, thus potentially conferring increased protection against emerging variants. 5–7 However, it remains unclear whether the mucosal IgA response elicited by vaccination or infection is protective against new omicron subvariants such as BA. 2.86.

In this Correspondence, we evaluated the level and breadth of mucosal antibody responses against the currently circulating variants in a study cohort comprising 15 vaccinated individuals, 13 of whom had confirmed breakthrough infection (appendix p 2). The infections occurred mainly during the waves of BA. 1, XBB, and BQ. 1 (appendix p 6). Matched saliva, nasal fluid, and tear samples from 15 participants (n= 45), together with matched serum samples from 11 participants, were