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BACKGROUND: Although recent epidemiological data suggest that pneumococci may contribute to the risk of SARS-CoV-2 disease, cases of co-infection with Streptococcus pneumoniae in COVID-19 patients during hospitalisation have been reported infrequently. This apparent contradiction may be explained by interactions of SARS-CoV-2 and pneumococcus in the upper airway, resulting in the escape of SARS-CoV-2 from protective host immune responses. METHODS: Here, we investigated the relationship of these two respiratory pathogens in two distinct cohorts of a) healthcare workers with asymptomatic or mildly symptomatic SARS-CoV-2 infection identified by systematic screening and b) patients with moderate to severe disease who presented to hospital. We assessed the effect of co-infection on host antibody, cellular and inflammatory responses to the virus. RESULTS: In both cohorts, pneumococcal colonisation was associated with diminished anti-viral immune responses, which affected primarily mucosal IgA levels among individuals with mild or asymptomatic infection and cellular memory responses in infected patients. CONCLUSION: Our findings suggest that S. pneumoniae impairs host immunity to SARS-CoV-2 and raises the question if pneumococcal carriage also enables immune escape of other respiratory viruses and facilitates reinfection occurrence. TRIALS REGISTRATION: ISRCTN89159899 for FASTER study and identifier: NCT03502291 for LAIV study.

Original publication




Journal article


J Clin Invest

Publication Date



Adaptive immunity, Bacterial infections, Immunology, T cells, Virology