Vaccination, which stimulates protective immune responses against acute and chronic infectious diseases, has been proved as one of the greatest achievements in public health. Vaccination saves lives. In the United States, with the help of vaccination, the incidences of a number of infectious diseases, including smallpox, measles, polio, rubella, pertussis, mumps, and diphtheria, have been successfully reduced by more than 90% with some of them being completely eradicated (i.e., smallpox) or nearly eradicated (percent decrease > 99%, such as polio and measles) (Orenstein et al., 2017). Vaccines against SARS-CoV-2 have been developed, deployed, and administered at a record speed with the aim to put the COVID-19 pandemic under control. To date, over....