Study finds vaccine side effects rare, outweighed by immunization benefits.

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Serious complications related to vaccines are very rare, and there is no evidence that immunizations cause autism, according to an analysis of 67 research studies.

The analysis comes as many vaccine-preventable diseases are making a comeback, often in communities with low vaccination rates. At least 539 people across 20 states have been infected with measles this year, according to the Centers for Disease Control and Prevention.

"This report should give parents some reassurance," says pediatrician Courtney Gidengil of Rand and Boston Children's Hospital, co-author of the study out today in Pediatrics.

The report says there is "strong evidence" that the measles vaccine is not associated with an increased risk of autism. That myth gained popularity in 1998 because of a medical study that has been retracted. Still, the myth persists.

"There is a lot of misinformation out there about vaccines," says co-author Margaret Maglione, also a researcher with Rand. "With the rise of the Internet and the decline of print journalism, anyone can put anything on the Internet."

Like all drugs, vaccines can cause serious side effects. But those complications are "extremely rare" and should be weighed against vaccination's enormous benefits, Maglione says.

In an April report, the CDC noted that vaccines given to infants and young children over the past two decades will prevent 322 million illnesses, 21 million hospitalizations and 732,000 deaths over the course of their lifetimes.

The new report notes that some vaccines, including flu shots and the combined vaccine against measles, mumps and rubella, are associated with an increased risk of fever-related seizures in small children. Although these seizures can be frightening for parents, they're typically benign and cause no long-term problems.

According to the analysis, vaccines against rotavirus – a common cause of severe diarrhea and dehydration in children – increase the risk of a serious type of intestinal blockage called intussusception, in which part of the intestine telescopes into itself. The vaccines against it, RotaTeq and Rotarix, can cause an additional one to five cases of intussusception for every 100,000 doses given, the analysis says.

It's important to remember that rotavirus infection also causes intussusception, says pediatrician Paul Offit, chief of infectious disease at Children's Hospital of Philadelphia and a developer of the RotaTeq vaccine. He notes that rates of this complication are actually down slightly since the introduction of the vaccines.

The new analysis may not convince parents who are strongly anti-vaccine. University of Utah pediatrician Carrie Byington says she hopes it will persuade doctors to promote vaccines to their patients.

In an accompanying editorial, Byington notes that recent medical school graduates are more skeptical about the effectiveness of vaccines than older doctors, who have been around long enough to have treated children for measles and meningitis. In Washington state, a study found that more than half of medical providers were willing to consider untested, alternative immunization schedules that skip or space out vaccines.

Doctors say it's important to put risks into perspective.

Nearly 38,000 children under age 4 were injured in car accidents in 2012, and 523 died, according to the CDC.

"The most dangerous aspect of giving your child vaccines is driving to the office to get them," Offit says.

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