CD9 and COVID-19: Interestingly, differential expression analysis showed that although a great number of proteins showed upregulation in CD9+-EVs of severely affected individuals at the infection peak (m0), only eight proteins were significantly different (four upregulated and four downregulated) in the convalescent state, suggesting that after symptoms remission, CD9+-EVs cargo in severe COVID-19 remain similar to that of the acute infection peak (Figure 6A).