In all the time I’ve covered health and medicine issues, nothing has been more polarizing than the debate over childhood immunizations. And while scientific evidence continues to mount against a causal connection between vaccines and developmental disorders such as autism, there was one concern voiced by some parents that seemed to make some sense to me: could the sheer number of shots that toddlers receive — often up to half a dozen at a single doctor’s visit — before they reach two years affect their health in a negative way? Intuitively, it makes sense that bombarding a still developing immune system with so many new pathogens to fight may not be such a good thing.
That’s exactly why researchers at University of Louisville decided to compare, for the first time, the cognitive outcomes of children who receive the normal schedule of shots and those whose parents chose to spread out the timing of their children’s immunizations, the goal being to reduce the immunological burden on their young bodies. Reporting in Pediatrics, a publication of the American Academy of Pediatrics, they found that the regular schedule of shots did not adversely impact children’s later scores on a series of cognitive tests — and conversely, that the children receiving spread out vaccines did not appear to enjoy any benefits or improvements on these measures seven to 10 years later.
The authors collected data from a previous study investigating thimerosal exposure from vaccines during the first year of life (thimerosal is a mercury-based preservative that is no longer used in childhood vaccinations except for the flu vaccine) and cognitive outcomes when the children were seven to 10 years old. The study involved 42 different assessments on a series of measures, including speech, language, memory, fine motor skills, intellectual functioning and attention. The authors grouped 1,047 children into those who received their full complement of childhood vaccinations on time, and those who either delayed or failed to receive all of their shots in the recommended time. Because the study was a retrospective investigation, the reasons for the delayed immunizations varied from unintentional omissions because the parents were either too busy or forgot to follow up with scheduled vaccinations, to intentional attempts to distance the time between shots.
After analysis, the researchers found that youngsters receiving their immunizations on time scored better than the other group on two measures, and that overall, the two populations scored about the same on the performance tests.
The data suggest that the concern about crowding vaccines into a short time period may be unfounded, and, should at least begin to alleviate parents’ concerns about the volume of shots infants receive.
