In Brief: Thimerosal exposure and neuropsychological development
Thimerosal exposure and neuropsychological development
In 1999, concerned about the health effects of mercury exposure, the U.S. Public Health Service and the American Academy of Pediatrics urged manufacturers to remove the preservative thimerosal (a mercury-containing preservative) from infant vaccines. Some retrospective analyses by the Centers for Disease Control and Prevention (CDC) suggested that early thimerosal exposure might cause language delays and a greater likelihood of developing tics.
However, the CDC has reported the results of a study that assessed neuropsychological abilities in children who had, earlier in their lives, been injected with vaccines containing thimerosal. The CDC concluded that early thimerosal exposure did not cause neuropsychological problems later on.
The CDC researchers enrolled 1,047 children ages 7 to 10, who were recruited from health maintenance organizations (HMOs). The researchers used standard instruments to assess 42 neuropsychological traits and abilities, such as speech, motor coordination, behavior regulation, and attention. Because children could participate in the study only if they had been enrolled in the same HMO from birth through their first birthdays, the researchers could also obtain their immunization records.