Delaying vaccinations won't help child's neurodevelopment

Kentucky pediatricians often ask Michael Smith, MD, a pediatric infectious disease specialist in Louisville, how to address parents' concerns that babies receive too many vaccines too soon.

Some parents choose to delay, or forgo, vaccines because of worries that vaccines given on the recommended schedule could overburden and weaken an infant's immune system and cause neurodevelopmental disorders or other illnesses.

Dr. Smith suggests physicians tell parents that putting off immunizations increases children's risk of contracting vaccine-preventable diseases, which can be fatal. Now he also plans to tell doctors there is no neuropsychological benefit to delaying vaccinations -- a finding from a study he co-authored that was published online in Pediatrics May 24.

"By delaying vaccines, [parents] think it's somehow safer. This study shows it's really not safer, at least in terms of neurodevelopment," said Dr. Smith, study lead author and assistant professor of pediatrics at the University of Louisville School of Medicine.

Researchers examined data on 1,047 children who were born between 1993 and 1997 and were part of a previous Vaccine Safety Datalink study on the safety of immunizations with thimerosal.

In 2003 and 2004, the children underwent 42 neuropsychological tests that assessed speech and language, verbal memory, motor coordination, behavior regulation and general intellectual functioning, among other things.

About half of the study participants had received all vaccines recommended by the Centers for Disease Control and Prevention on time during their first year of life. Researchers considered the vaccines on time if they were received within 30 days of the age recommended by the CDC.

Twenty-three percent got vaccines by their first birthday but on a different schedule. Another 20% did not receive all immunizations recommended for the first year. Fewer than 1% received no vaccines during the study period.

Researchers performed two analyses. The first compared children who received vaccines within 30 days of the recommended age to those who had at least one dose delayed. In the second analysis, children who received the most vaccines during their first seven months were compared with those who received the fewest.

No benefits were found for children with delayed vaccines, or for those who received fewer vaccinations than were recommended. In fact, children who were immunized on time scored slightly better on two of the neuropsychological tests, after adjusting for family and socioeconomic factors, than did children whose vaccines were delayed.

The study does not answer "the big question" that parents have about whether there is a difference in long-term health among children who are vaccinated and those who do not receive any immunizations, said Barbara Loe Fisher. She is co-founder and president of the National Vaccine Information Center, a nonprofit educational organization based in Vienna, Va.

The CDC recommends that babies receive 18 to 21 doses of 10 vaccines by their first birthdays. The varied dose recommendations are due largely to the requirements of different vaccine brands. For example, children need two or three doses of the rotavirus vaccine, depending on which brand they receive.