Vaccinating your child is the one way that you can shield them from getting some seriously harmful diseases. But did you know that when you vaccinate your child you are also helping to keep other children safe from harmful diseases? You are! And you are especially helping prevent disease in those children who are too sick to get vaccines for themselves. A phenomenon called herd immunity occurs when most of the people in a community are vaccinated against a disease, leaving no one to carry it, and thus, protecting those people who cannot be vaccinated. This way, even those who are not eligible for certain vaccines—such as babies, pregnant women, or people who are sick with immune system-compromising illnesses—get some protection.