Nearly one in seven public and private schools have measles vaccination rates below 90%, a rate considered inadequate to provide immunity, according to USA Today's analysis of immunization information in 13 states.
Meghan Hoyer and Steve Reilly write that hundreds of thousands of US students attend schools where vaccination rates are even lower, sometimes under 50%. It appears that those who are opposed to vaccinations tend to live in proximity of each other, meaning that some schools are dangerously vulnerable even while other schools are completely protected.
Some of the clusters are made up of a number of people who have philosophical objections to vaccines, including some in lower-income neighborhoods where parents can often not afford to keep up with their children's vaccinations.
Now, the nation is in the middle of a serious outbreak that has more than 100 people in 14 states suffering. The CDC has repeatedly recommended that states keep records of immunization rates, though few do.
"Really, what should concern parents is the microclimate of their child's school or day care center. And we just had no information about it," said Sundari Kraft, who helped push through a Colorado bill last year requiring schools to provide vaccination rates to anyone who asks. The state does not collect or analyze the data.
"We want to look at ways we can better protect our children before we experience a health crisis," she said.
States including Arizona and California have relatively low vaccination rates because of increasing use of non-medical exemptions, which have caused both states to have a nearly 70% increase in exemptions from 2009 to 2013. Philosophical or religious exemptions have increased 37% nationwide, according to the CDC. To not be vaccinated poses a threat to the broader population by way of schools, bus terminals, hospitals, and other public venues.
Saad Omer, an epidemiologist and professor at Emory University who studies immunizations, explained "herd immunity." To protect the infants and those with immune deficiencies, as many as are able to be vaccinated need to do so. A cluster of people who do not get vaccinated become a mass of individuals who are susceptible, which can trigger an outbreak.
Even so, there is no perfect immunity.
"If a vaccine is, let's say, 80% efficacious, there's a â¦ 1 in 5 chance that even if you do the right thing, your kid is unprotected," Omer said.
The anti-vaccine movement can be traced, in large part, to a report in 1998 published in a medical journal that theorized that vaccines and autism could be linked. The report was later debunked, but many parents still believe it.
There are those, like some Amish sects, who disagree with vaccinations on religious grounds, and there are the wealthy, well-educated families who want their children to live "all-natural" lives and reject the vaccines' toxins, write Jack Healy and Michael Paulson reporting for The New York Times.
California lawmakers this week introduced a bill that would prohibit opting out of vaccinating schoolchildren. Exemptions for children who are medically unfit to be vaccinated, however, will continue to be exempt. The personal belief waiver, however, will be removed, which means that California will have stricter rules concerning vaccines than all states but Mississippi and West Virginia. The San Diego Union-Tribune's Chris Nichols quotes one lawmaker:
The outbreak at Disneyland infected those from 7 months to 7 years old, including five Disneyland workers.
For a year now, California parents have had to meet with a licensed physician, nurse practitioner, physician assistant, naturopathic doctor, or credentialed school nurse before they could opt out. The health providers were required to share information about the benefits of immunization, and if parents still wanted to opt out, they were required to submit a note from a health provider.
NBC News reporter Maggie Fox writes that Colorado has the highest rates of under-immunized children, according to the CDC.