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CD4+ T cells reactive against SARS-CoV-2 can be found in unexposed individuals and these 43 are suggested to arise in response to common cold corona viruses (CCCoVs) infection. 44 Here, we utilized SARS-CoV-2-reactive CD4+ T cell enrichment to examine the antigen-45 avidity and clonality of these cells, as well as the relative contribution of CCCoV cross-46 reactivity. SARS-CoV-2-reactive CD4+ memory T-cells were present in virtually all 47 unexposed individuals examined, displaying low functional avidity and multiple, highly 48 variable cross-reactivities that were not restricted to CCCoVs. SARS-CoV-2 reactive CD4+ T 49 cells from COVID-19 patients lacked cross-reactivity to CCCoVs, irrespective of strong 50 memory T-cell responses against CCCoV in all donors analysed. In severe but not mild 51 COVID-19, SARS-CoV-2-specific T-cells displayed low functional avidity and clonality, 52 despite increased frequencies. Our findings identify low avidity CD4+T cell responses as a 53 hallmark of severe COVID-19, and argue against a protective role for CCCoV reactive T cells 54 in SARS-CoV-2 infection.