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Simple Summary: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the pandemic coronavirus disease-2019 (COVID-19), which can lead to severe pneumonia and acute respiratory distress syndrome (ARDS). The immune system plays a key role in the defense against COVID-19. Nonetheless, if dysregulated and hyperactivated, the immune response can trigger the deleterious "cytokine storm". Multiple studies are aimed at finding potential immunomodulators to rebalance the immune response against the virus, thus limiting its dangerous effects. Moreover, the development of vaccines against SARS-CoV-2 has represented a global challenge. The aim of this narrative review is to describe the state-of-the-art knowledge on the immune system response in COVID-19 and to underline the main therapeutic strategies and the key role of vaccines. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative pathogen of coronavirus disease 19 (COVID-19). COVID-19 can manifest with a heterogenous spectrum of disease severity, from mild upper airways infection to severe interstitial pneumonia and devastating acute respiratory distress syndrome (ARDS). SARS-CoV-2 infection may induce an over activation of the immune system and the release of high concentrations of pro-inflammatory cytokines, leading to a "cytokine storm", a recognized pathogenetic mechanism in the genesis of SARS-CoV-2-induced lung disease. This overproduction of inflammatory cytokines has been recognized as a poor prognostic factor, since it can lead to disease progression, organ failure, ARDS and death. Moreover, the immune system shows dysregulated activity, particularly through activated macrophages and T-helper cells and in the co-occurrent exhaustion of lymphocytes. We carried out a non-systematic literature review aimed at providing an overview of the current knowledge on the pathologic mechanisms played by the immune system and the inflammation in the genesis of SARS-CoV-2-induced lung disease. An overview on potential treatments for this harmful condition and for contrasting the "cytokine storm" has also been presented. Finally, a look at the experimented experimental vaccines against SARS-CoV-2 has been included. [ABSTRACT FROM AUTHOR]