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San Diego Study: California Kids With An Autistic Older Sibling Are Less Likely To Be Vaccinated

In this file photo, a pediatrician holds a dose of the measles-mumps-rubella ...

Credit: Associated Press

Above: In this file photo, a pediatrician holds a dose of the measles-mumps-rubella (MMR) vaccine at his practice in Northridge, Calif., Thursday, Jan. 29, 2015.

San Diego researchers are out with a new study that finds California kids are less likely to be vaccinated if they have an older sibling with autism.

Published Thursday in the New England Journal of Medicine, the analysis of more than 200 Southern California families reveals that only 83 percent of infants with an autistic older sibling are vaccinated, compared with 97 percent of infants in general.

The researchers found that families with an autistic child started off just as likely to vaccinate their first kid as families without an autistic child. But a wide gap opened up among younger siblings.

"It does show that these families are changing their vaccination behaviors with subsequent children," said lead author Gena Glickman, a researcher at UC San Diego.

"Autism and vaccines continue to be linked in the minds of some, despite overwhelming evidence to the contrary. So that could be what's going on," she said.

Glickman and her colleagues were not originally focused on vaccines. They began studying siblings of autistic children in 2009 with the hope of pinpointing biomarkers for the disorder.

But as California increasingly became an epicenter of the debate over whether parents should be allowed to opt their children out of vaccines due to personal beliefs, the researchers became interested in tracking vaccination rates within this group of kids.

When asked about their experience with vaccines, parents of autistic children were more likely to say that their kids had experienced adverse reactions, such as fevers and rashes.

Glickman emphasized that these adverse reactions were self-reported. Parents could have been biased in how they recalled these episodes. And the symptoms they observed in their children could have had nothing to do with vaccines. But these concerns may offer an explanation for why certain parents become less likely to vaccinate, Glickman said.

"Maybe it has nothing to do with concerns about autism at all. But rather, they are just worried about these other types of adverse reactions," she said.

Due to a state law approved in 2015, California parents can no longer cite personal beliefs to avoid vaccinating their children. Vaccination rates among kindergartners rose after the law's passage. But there has also been a recent spike in medical exemptions in the state, suggesting some parents are still finding ways to skip shots for their kids.

Glickman worries that if parents are not engaged on this issue, vaccination rates could remain low for the siblings of autistic children.

"I think there are a lot of people in the scientific community who would just like to lay this to rest," she said. "But I don't think it's going away anytime soon. And we need to figure out how to handle it."

Only 83 percent of infants with an autistic older sibling are vaccinated, compared with 97 percent of infants in general.

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