Measles vaccination coverage has steadily declined since the beginning of the COVID-19 pandemic. In 2021, a record high of nearly 40 million children missed a measles vaccine dose: 25 million children missed their first dose and an additional 14.7 million children missed their second dose, a joint publication by the World Health Organization (WHO) and the United States Centers for Disease Control and Prevention (CDC) reports. This decline is a significant setback in global progress towards achieving and maintaining measles elimination and leaves millions of children susceptible to infection.