According to the Centers for Disease Control & Prevention (CDC):
Vaccine-preventable disease levels are at or near record lows. However, we cannot take high immunization coverage levels for granted. Vaccine-preventable diseases such as polio, chickenpox, whooping cough, measles, and diphtheria are not diseases of the past. They are still circulating either at low levels in the United States or at epidemic levels elsewhere in the world – only a plane ride away. Someone leaving India yesterday could very easily pass along the polio virus to unvaccinated children in the United States today. If vaccination coverage levels drop, we can expect a resurgence of many of these diseases, along with the suffering and death that they can cause. Immunizations are one of the best ways that parents can protect their children against serious diseases. We must obtain maximum immunization coverage in all populations, implement immunization systems, and ensure vaccine safety.