According to a new report in the Journal of Pediatrics, vaccines are not associated with an increased risk of developing autism. After analyzing records from more than 1000 children the researchers found no link between the amount of antigen exposure and later developing autism. NBC's Dr. Nancy Snyderman reports.

A new study adds to years of research showing that childhood vaccines do not cause autism, despite worries among a growing number of parents that their young children receive “too many vaccines.”

Researchers from the Centers for Disease Control and Prevention concluded that even when multiple inoculations are given on the same day, children are at no higher risk of developing autism, according to the report published in the Journal of Pediatrics Friday.

“This study looked into the concern that receiving too many vaccines at one doctor’s visit or too many vaccines during the first two years of life may be linked to the development of autism,” the report’s lead author, Dr. Frank DeStefano told NBC chief medical editor Dr. Nancy Snyderman. “We found they’re not related.”

The CDC researchers conducted the study by reviewing the vaccination histories collected between 1994 and 1999 of 256 children with autism and 752 children who did not have the disorder. They calculated the number of antigens – the substances in a vaccine that stimulate disease-fighting antibodies – that infants are exposed to either on one doctor’s visit or overall during the first two years.

“We did not find any relationship between the number of antigens and the risk of autism,” said DeStafano, Director of the Immunization Safety Office at the CDC.

The CDC study comes amidst reports that increasing numbers of parents are delaying or skipping childhood inoculations, fearing side effects or the risk of autism and other learning disabilities.

A 2012 study, which examined medical records for 97,711 Portland, Oregon children, found an almost four-fold increase between 2006 and 2009 in the percentage of parents who delayed or skipped vaccinations, researchers reported in the journal Pediatrics. Experts say that by delaying certain vaccinations, parents may be putting their children -- and those of others -- at a far greater risk of contracting deadly diseases, such as pneumonia and whooping cough, also known as pertussis. In 2012, the US experienced the worst epidemic of whooping cough in 50 years

That’s a real concern for Dr. Tanya Altmann, an assistant clinical professor at Mattel Children’s Hospital at UCLA.

“Some parents ask about waiting on vaccines and using an alternative or delayed schedule,” because of worries about autism, Altmann told Snyderman.

Altmann tries to remind parents that while they may worry about the unknown, there are real risks to skipping vaccinations or delaying them: outbreaks of severe, sometimes deadly, illnesses.

“The bottom line for parents is that these outbreaks are real and they will come back,” Altmann said. “These are serious illnesses, meningitis, whooping cough. This study is just one more piece of evidence to reassure parents that vaccines are safe.”

Although inoculation contents and schedules have changed since the study data was collected, Snyderman sees the findings as applicable to today's children since CDC researchers tallied the total amount of antigens -- bits of protein in a vaccine that spark an immune response -- that each child was exposed to.

“While the CDC now recommends more vaccinations than it did in the 90s, the level of antigens in today’s vaccines is markedly lower than it was when this data was collected,” Snyderman said.

DeStefano hopes the new research will convince parents that it’s safe to follow CDC vaccination schedules.

“The number of vaccines in the current immunization schedule is what’s needed to protect children,” he said. “It’s not too many for a child’s immune system.”

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