Methods: The prospective birth cohort study with sample consisted of 369 infants born in Krakow. Vaccination
history against measles (date and the type of the vaccine) was extracted from physicians’ records.
Child development was assessed using the Bayley Scales of Infant Development (BSID-II) up to 3rd year
of life, Raven test in 5th and 8th year and Wechsler (WISC-R) in 6th and 7th year. Data on possible confounders
came from mothers’ interview, medical records and analyses of lead and mercury level at birth
and at the end of 5th year of life. Linear and logistic regression models adjusted for potential confounders
were used to assess the association.