(RxWiki News) The Centers for Disease Control and Prevention regularly update the recommendations for children's shots to help parents better understand new vaccinations. Some parents may be concerned that children receive more vaccines today than they had when the parents were young.
Yet what matters is not the number of shots — but what is in the shots.
A recent study found no negative long-term mental effects in children based on their exposure to the substances in vaccines that make the body build resistance to a disease.
"Ask your child's pediatrician about vaccines."
This study, led by Shahed Iqbal, of the Immunization Safety Office at the Centers for Disease Control and Prevention (CDC), looked at whether the number of antigens children receive in all their vaccines is linked to neurological or psychological issues.
An antigen is the substance in vaccines that causes the immune system to develop antibodies to fight the disease.
An antigen could be a killed virus, a piece of bacteria, a protein from the germ or another variation of the disease that tricks the body into thinking it needs to build up antibodies to fight the disease.
The researchers analyzed the vaccination histories, through age 2, of 1,047 children and compared the histories to the children's neurological and psychological characteristics at ages 7 to 10.
The children underwent standardized tests that specifically measured their general intelligence, speech and language, verbal memory, achievement, visual spatial ability, ability to regulate their behavior, tics, attention and overall executive function.
Executive function refers to a collection of cognitive activities, including memory, organization, planning, problem solving, verbal reasoning, mental flexibility, multi-tasking and self-control.
The researchers estimated that the children had been exposed to an average 7,266 antigens from their combined vaccinations by the time they were 7 months old.
By the time they were 1 year old, the children had been exposed to an average 8,127 antigens in total.
By age 2, they had been exposed to an average 10,341 total antigens from all their immunizations up to that point, based on their immunization histories.
For each additional 1,000 antigens the children were exposed to, the researchers found no evidence of differences in neurological or psychological outcomes.
When the researchers compared the children with the highest exposure to antigens to the children with the lowest antigen exposure, they also did not find any negative mental issues in either group of children.
In fact, the children who had been exposed to the highest amount of antigens — in the top tenth percentile — actually performed about twice as well on attention and executive function tests as the children in the lowest tenth percentile.
However, that positive finding does not necessarily mean that greater exposure to antigens was more protective of kids' mental abilities.
The researchers would need to do more research to determine whether other factors accounted for those improved scores or if the higher scores were actually related to the antigens the children had received.
Thomas Seman, MD, a dailyRx Contributing Expert and a pediatrician at North Shore Pediatrics in Danvers, Mass., said this study is important because of its focus.
"It's nice to see a well created study to look at the rate of immunization and overall health," Dr. Seman said. "People have focused on the number of immunizations and not the amount of antigens — the particle to which the body responds and makes an antibody."
But the number of shots a child gets can be misleading in terms of what children are exposed to.
"The article demonstrates that the number of antigens is actually significantly lower with the newer vaccines," Dr. Seman said. While children may get a higher number of total vaccines today than they did in years past, the number of total antigens they get has dropped.
"Therefore, the immunological stress on the child who is vaccinated is actually less now than before," Dr. Seman explained.
And the effect of widespread vaccination is widespread reduction in disease.
"Without these sometimes deadly, yet frequently overwhelming illnesses prevalent in the community, children can grow and develop to the best of their abilities," Dr. Seman said. "When children's bodies are healthy, their brains are healthier and able to think more clearly."
Dr. Seman suggested that perhaps the healthier bodies of children with higher antigen exposure might relate to the researchers' findings about executive function.
"Less stressed bodies are calmer, less likely to respond to stimuli with anxiety and therefore are more likely to be able to focus and have better executive function, which allows them to organize themselves, their work and their world and work more effectively," Dr. Seman said.
"The newer vaccines since the mid-1990s are cleaner, with fewer remnants from the organism used for the vaccine and fewer antigens present," he said. "The final take is 'Vaccinate!'"
This study was published July 12 in the journal Pharmacoepidemiology and Drug Safety. The research was funded by the CDC. The authors reported no conflicts of interest.