Study debunks a common autism worry about vaccines

When speaking with parents about vaccinations, physicians have new scientific evidence that the number of vaccines children receive between birth and age 2 are not associated with the risk of autism.

After looking at how many antigens children received on a single day of vaccination and the total number of antigens they received during their first two years, researchers concluded there was no link between the vaccines and developing autism spectrum disorder.

Study authors used data from three managed care organizations to compare 256 children with ASD and 752 children without ASD, and found children in each group received the same number of antigens. They also found that children with ASD with regression did not receive more antigens than children without ASD with regression, according to the study posted online March 29 in The Journal of Pediatrics.

“This reinforces the importance of parents having their children vaccinated,” said study lead author Frank DeStefano, MD, MPH, director of the Centers for Disease Control and Prevention’s Immunization Safety Office. “This should help alleviate fears.”

The research is the latest of nearly a dozen studies on the link between autism and vaccines the CDC has published in the past decade. None of them has shown a link between vaccines and autism.

“Parents concerns have evolved,” Dr. DeStefano said. “It started with the [measles, mumps and rubella] vaccine 15 years ago. The evidence became convincing that there was not a link between the vaccine and autism. After that, the concern was thimerosal. Again, the evidence on that concluded there was no causal association. … This addresses the latest evolution of concern that there are too many vaccines too soon.”

The study noted that the 2012 routine childhood schedule has several more vaccines than the schedule in the late 1990s, when the children in the study received their vaccines. However, children today are exposed to fewer antigens because of changes in the vaccines.

“The maximum number of antigens to which a child could be exposed by age 2 was 315 in 2012, compared with several thousand in the late 1990s,” the study said.

Talking with parents

Rochester, N.Y., pediatrician Susan L. Hyman, MD, chair of the autism subcommittee of the American Academy of Pediatrics’ Council on Children with Disabilities, said the new study provides important information for physicians and others counseling and educating families.

“No one study will calm people who are worried, but it calms physicians,” Dr. Hyman said.

Study authors noted that a 2011 study published in Pediatrics found that 10% of parents of young children refuse or delay vaccinations, with most believing that delaying vaccine doses is safer than providing them on the CDC’s recommended vaccination schedule. A 2011 Health Affairs study showed that 30% to 36% of parents were concerned about too many vaccines being administered during the first two years of life, too many vaccines being administered in a single doctor visit and a possible link between vaccines and learning disabilities, such as autism. That number jumped to 55% to 90% among parents who told researchers their children would receive some but not all of the vaccines on the recommended schedule.

Dr. Hyman said physicians need to be partners in their patients’ education about vaccines, and the time to educate is before resistance emerges.

“Fear is very difficult to counteract,” Dr. Hyman said. “We need to work with families to prevent preventable childhood illness.”

She said physicians should counsel patients by sharing knowledge with them and not counteracting fear with fear. “We want parents to understand the science and to make informed decisions,” Dr. Hyman said.

Kansas City, Mo., emergency pediatrician Sharon G. Humiston, MD, MPH, said physicians should be sensitive to a parent’s needs.

“Some parents need data. For those parents, physicians need to be able to summarize the data,” said Dr. Humiston, co-author of the book Vaccinating Your Child: Questions and Answers for the Concerned Parent. “Physicians also need to recognize that some parents don’t trust science and we need to talk about our personal experience. … Physicians can’t lose sight of the fact that more data isn’t going to be enough for all parents.”

Barbara Loe Fisher, co-founder and president of the consumer-led National Vaccine Information Center, said the new CDC study “does nothing to reassure parents” that administering a large number of vaccines is safe and unrelated to the increase in autism. She said the study lacked a control group of unvaccinated children and ignored how genetic variation and biological differences between children can affect individual susceptibility to vaccines.

“There is an urgent need for a well-designed, prospective long-term study that includes vaccinated and unvaccinated infants and children conducted by nonindustry, nongovernmental investigators to evaluate not only all morbidity and mortality outcomes, but also to measure pathological changes in the brain and immune function over time in both groups,” Fisher said.

Dr. Humiston said concerns among parents are natural.

“It is very understandable that parents would be fearful because the CDC is finding out that the number of kids with autism spectrum disorder is enormous,” she said. “The real answer to autism is in science and we, as the pediatric community, as well as the scientific community … need to really be delving into the grassroots causes.”