The phrase "immunization rates" refers to the percentage or number of people who have received required vaccinations to protect against different diseases. Full definition
Pertussis is a highly contagious and potentially fatal vaccine - preventable disease that has re-emerged in the United States despite high childhood immunization rates. (sciencedaily.com)
Communities depend on high immunization rates to keep vaccine - preventable diseases from spreading. (caringforkids.cps.ca)