Abstract: Inoculation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in populations is very important for the prevention and control of coronavirus disease 2019 (COVID-19) pandemic and currently many types of COVID-19 vaccines, including mRNA, recombinant protein, adenovirus vector and inactivated virus vaccine, have been approved worldwide. The results of clinical trials and real-world studies have demonstrated that the candidate vaccines are safe and effective. Meanwhile, the protective effect of the vaccines on specific subgroups, such as the elderly, pregnant or lactating women, patients with cancer or autoimmune diseases, still needs to be further studied. In addition, the effectiveness of the vaccines against the mutated strains of SARS-CoV-2 increasingly prevalent worldwide remains to be observed. The literature study reviews researches on efficacy and safety of COVID-19 vaccine, especially its protective effect in specific populations and the people infected by variant SARS-CoV-2 strains.