When allowing some dissimilarity, VZV has the highest number of SARS-CoV-2 like epitopes. However, this we only find for HLA-I, and in particular HLA-B and HLA-C, but not for HLA-II. Since SARS-CoV-2 specific T cells are found among both the HLA-I reactive CD8+ and among the HLA-II reactive CD4+ it is not likely that VZV is the pathogen behind the SARS-CoV-2 cross reactive T cells. Rather, only the endemic coronaviruses, and in particular the beta-coronaviruses, have the highest number of epitopes similar to those predicted in the SARS-CoV-2 virus. However, the similarity between epitopes from SARS-CoV-2 and endemic coronaviruses was concentrated in replication related proteins. Thus, it appears unlikely that endemic coronaviruses should give rise to the observed preformed T cell immunity towards the S-protein. This notion is supported by experimental findings, where cross-reactivity to S-protein is rare24,40. A set of near-identical SARS-CoV-2 epitopes have been identified in Mycobacterium bovis27 which, in its attenuated form, is used as vaccine against tuberculosis. Although the efficacy of this vaccine against SARS-CoV-2 remains unclear41,42, the findings indicate nonetheless that SARS-CoV-2 cross-reactive T cells can have sources widely different from viral pathogens.