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Abstract Pronounced immune escape by the SARS-CoV-2 Omicron variant has resulted in many individuals possessing hybrid immunity, generated through a combination of vaccination and infection. Concerns have been raised that omicron breakthrough infections in triple-vaccinated individuals result in poor induction of omicron-specific immunity, and that prior SARS-CoV-2 infection is associated with immune dampening. Taking a broad and comprehensive approach, we characterize mucosal and blood immunity to spike and non-spike antigens following BA.1/BA.2 infections in triple mRNA-vaccinated individuals, with and without prior SARS-CoV-2 infection. We find that most individuals increase BA.1/BA.2/BA.5-specific neutralizing antibodies following infection, but confirm that the magnitude of increase and post-omicron titres are higher in the infection-naive. In contrast, significant increases in nasal responses, including neutralizing activity against BA.5 spike, are seen regardless of infection history. Spike-specific T cells increase only in infection-naive vaccinees; however, post-omicron T cell responses are significantly higher in the previously-infected, who display a maximally induced response with a highly cytotoxic CD8+ phenotype following their 3rd mRNA vaccine dose. Responses to non-spike antigens increase significantly regardless of prior infection status. These findings suggest that hybrid immunity induced by omicron breakthrough infections is characterized by significant immune enhancement that can help protect against future omicron variants.

Understanding the immune response to SARS-CoV-2 is dependent on being able to distinguish COVID-19 immune responses from cross-reactive immune responses to other coronaviruses. Here the authors show that choice of antigens and whether an ICS, ELISPOT or T cell proliferation assay is used has a major effect on this discriminatory ability.

Dengue (DENV) and Zika (ZIKV) viruses normally display as smooth spherical particles, while DENV can also become bumpy-surfaced, resulting in immune evasion. Here, Morrone et al. report DENV and ZIKV infectious club-shaped particles (clubSP) that display distinct antibody binding properties.