Development of an effective vaccine requires a long and complicated process. Preclinical studies and phase , , clinical trials mainly focused on the assessment of the vaccine's safety (tolerability), immunogenicity and efficacy before license. After license, it is necessary to further evaluate the actual effectiveness and safety in the general population through phase clinical trials and optimize the immunization strategies with the disease's epidemiology data. In this special issue, published several articles, which reported the main results of pre-license clinical trials and post-marketing evaluation of various vaccines, it was extremely useful to support vaccine licensing and market use. We encourage the continuous clinical studies and post-marketing evaluation of vaccines, including the novel corona virus-19 vaccines, to provide technical support for the population use, under the situation of COVID-19 pandemic.