Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)has caused more than 100 million cases of COVID-19 worldwide[1].The United States is still the country with the highest number of confirmed cases and deaths of COVID-19,with more than 25.5 million confirmed cases and more than 420,000 deaths[2],which exceeds the total number of American deaths in World War II.Since the outbreak of COVID-19 in 2020,countries have been actively developing an effective and safe vaccine to prevent COVID-19 and influence the course of the current pandemic.At present,there are more than 60 candidate vaccines against SARS-CoV-2 in clinical research around the world[3].