Why Immunizations Matter

A measles outbreak that began in January 2025 in west Texas and New Mexico underscores the critical role immunizations play in protecting public health. By mid-March, more than 250 cases had been identified — primarily among unvaccinated children — and the outbreak had resulted in the first measles-related death in the U.S. since 2015. This resurgence of a vaccine-preventable disease highlights the importance of immunization to safeguard individuals and communities from infectious diseases.

Immunizations are one of the most effective tools in preventing the spread of infectious diseases. Vaccines reduce illness and death while saving billions in healthcare costs. They work by strengthening the body’s immune response, protecting from harmful diseases such as measles, polio, and whooping cough. When enough individuals are vaccinated, communities can better protect those who cannot be vaccinated, including infants and people with certain medical conditions.

This explainer looks at how immunizations provide immunity against disease, the different types of vaccines, standards used to determine vaccine safety and effectiveness, and immunization recommendations.