- California lawmakers introduced a bill Wednesday that would require parents to vaccinate all school children unless a child's health is at risk, the Associated Press reported.
- The bill would leave in place only medical exemptions — for children who, for example, have weakened immune systems.
- The bill comes in response to the ongoing measles outbreak, which originated at Disneyland in California last December.
California would become third state without personal and religious exemptions
Only two other states don't have personal or religious exemptions for childhood vaccination requirements: West Virginia and Mississippi.
Less than 90 percent of California children ages 2 to 5 enrolled in the state's child-care facilities had all the required vaccinations at the start of the 2014-2015 school year, according to the California Department of Public Health. About 5 percent of the children not meeting vaccination requirements had a permanent medical exemption.
Almost everyone needs to get vaccinated for herd immunity
Widespread vaccine coverage is important because of what's known as herd immunity, a coverage threshold that effectively prevents an illness from spreading.
Vaccinated people essentially act as barriers to outbreaks, since diseases can't pass through them and infect others. This barrier helps protect some of the most vulnerable populations: infants under 12 months of age, who can't get vaccinated and are more susceptible to infection, and the elderly, who have a higher risk of death if they contract vaccine-treatable illnesses.
Herd immunity against measles requires as much as 94 percent of the population to be vaccinated, according to the Centers for Disease Control and Prevention.