Robocalls started going out last week to parents of children in northern California whose records show an insufficient number of mumps, measles and rubella vaccinations.
To be fully protected, every adult and every child over the age of five should have had two shots.
Kaiser Doctor Ken Hempstead says it's important for everyone to be vaccinated not only for themselves, but for others around them.
"If I have a child who's under 12 months of age, they're too young to get protection from the vaccine. If I have a child who is undergoing chemotherapy for cancer, they're not in a position where their immune system is robust enough to have protection from a vaccine.
Hempstead says vaccination is the only defense against "childhood" diseases.
"That's important for people to understand that there really isn't a good backup to vaccination. Once you have this, we obviously would do everything we can to help you through it, but we really don't have an antibiotic or medicine that's going to actively treat your disease."
if you are one of the rare adults who received only one vaccination as a child, you should visit a doctor for an antibody blood test.
The Centers for Disease Control says measles can cause pneumonia, encephalitis, and death.
Kaiser expects calls to Spanish-speaking parents to begin this week.
Kaiser Permanente Northern California covers the area from Fresno to Sacramento and west to Santa Rosa.