Updated: Apr 4
The goal of public health is to prevent disease. It's much easier and more cost-effective to prevent a disease than to treat it. That's exactly what immunizations aim to do.
Immunizations protect us from serious diseases and also prevent the spread of those diseases to others. Over the years immunizations have thwarted epidemics of once common infectious diseases such as measles, mumps, and whooping cough. And because of immunizations we've seen the near eradication of others, such as polio and smallpox.
Source: WebMD, https://www.webmd.com/children/vaccines/immunizations-vaccines-power-of-preparation