Vaccines are important because they 1) prevent severe disease and death 2) prevent even mildly symptomatic disease 3) prevent transmission of disease and 4) enable countries to reopen their economies. Vaccines were developed more than 200 years ago but in the 21st century, they are still recognized as a leading public health achievement, second only to reductions in child mortality, ahead of access to safe water and sanitation, and the prevention and control of malaria, tuberculosis and HIV/AIDS.
