Elsevier created a free COVID-19 resource center in January 2020, offering English and Mandarin information on the virus. The center allows free access to research in PubMed Central and other repositories for unrestricted use. A review discusses adaptive immunity to SARS-CoV-2 and COVID-19, highlighting the roles of B cells, CD4+ T cells, and CD8+ T cells in controlling the virus. The review emphasizes that CD4+ T cells, CD8+ T cells, and neutralizing antibodies contribute to controlling SARS-CoV-2 in both mild and severe cases. The adaptive immune response is slow, requiring time for naive cells to proliferate and differentiate. SARS-CoV-2 is effective at evading innate immune responses, particularly type I and III IFNs, leading to delayed adaptive immune priming. This delay can result in asymptomatic infections or mild disease. In severe cases, delayed innate immune responses lead to severe lung disease. CD4+ T cells are crucial for controlling infection, with their presence associated with reduced disease severity. CD8+ T cells also play a role in viral clearance. Neutralizing antibodies are important but their titers do not always correlate with reduced disease severity. SARS-CoV-2-specific CD4+ T cells are more prominent than CD8+ T cells. CD4+ T cells can differentiate into various effector cells, including Tfh cells, Th1 cells, and CD4-CTLs. These cells help B cells, recruit innate cells, and have direct antiviral activities. CD8+ T cells are critical for killing infected cells and are associated with better outcomes. Antibodies, particularly neutralizing antibodies, are important but their effectiveness varies. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells are more effective in controlling infection than neutralizing antibodies. The review also discusses the importance of adaptive immunity in preventing severe disease and the role of T cell responses in immune memory. Age is a major risk factor for severe COVID-19, with older individuals having a higher risk due to reduced naive T cell pools. Gender differences exist, with men at greater risk than women. The review highlights the complexity of adaptive immunity and the need for further research to understand immune responses and develop effective vaccines.Elsevier created a free COVID-19 resource center in January 2020, offering English and Mandarin information on the virus. The center allows free access to research in PubMed Central and other repositories for unrestricted use. A review discusses adaptive immunity to SARS-CoV-2 and COVID-19, highlighting the roles of B cells, CD4+ T cells, and CD8+ T cells in controlling the virus. The review emphasizes that CD4+ T cells, CD8+ T cells, and neutralizing antibodies contribute to controlling SARS-CoV-2 in both mild and severe cases. The adaptive immune response is slow, requiring time for naive cells to proliferate and differentiate. SARS-CoV-2 is effective at evading innate immune responses, particularly type I and III IFNs, leading to delayed adaptive immune priming. This delay can result in asymptomatic infections or mild disease. In severe cases, delayed innate immune responses lead to severe lung disease. CD4+ T cells are crucial for controlling infection, with their presence associated with reduced disease severity. CD8+ T cells also play a role in viral clearance. Neutralizing antibodies are important but their titers do not always correlate with reduced disease severity. SARS-CoV-2-specific CD4+ T cells are more prominent than CD8+ T cells. CD4+ T cells can differentiate into various effector cells, including Tfh cells, Th1 cells, and CD4-CTLs. These cells help B cells, recruit innate cells, and have direct antiviral activities. CD8+ T cells are critical for killing infected cells and are associated with better outcomes. Antibodies, particularly neutralizing antibodies, are important but their effectiveness varies. SARS-CoV-2-specific CD4+ T cells and CD8+ T cells are more effective in controlling infection than neutralizing antibodies. The review also discusses the importance of adaptive immunity in preventing severe disease and the role of T cell responses in immune memory. Age is a major risk factor for severe COVID-19, with older individuals having a higher risk due to reduced naive T cell pools. Gender differences exist, with men at greater risk than women. The review highlights the complexity of adaptive immunity and the need for further research to understand immune responses and develop effective vaccines.