California parents are deciding against vaccinating their kindergarten-age children at twice the rate they did seven years ago, a fact public health experts said is contributing to the reemergence of measles across the state and may lead to outbreaks of other serious diseases.
The percentage of kindergartens in which at least 8% of students are not fully vaccinated because of personal beliefs has more than doubled as well, according to data on file with the state. That threshold is significant because communities must be immunized at a high rate to avoid widespread disease outbreaks. It is a concept known as herd immunity, and for measles and whooping cough at least 92% of kids need to be immune, experts say.
State law requires kindergartners to be vaccinated against measles, pertussis ( whooping cough), polio, mumps, rubella, hepatitis B, chicken pox, diphtheria and tetanus.
Parents who say immunization is against their personal beliefs can get exemptions. Some opt out of all the mandatory shots, while others allow students to get select vaccinations. There are also temporary and medical exemptions.
That makes exact vaccination rates hard to assess. But the upward trend in belief exemptions is troubling to health experts. California is coping with a whooping cough epidemic and earlier this year experienced a cluster of measles outbreaks, thanks in part to insufficient vaccination.
The anti-vaccination movement is being driven by parents who question the medical consensus that inoculations are safe. Some are concerned that vaccines could trigger autism — a theory that has been thoroughly discredited by scientists.