SAN FRANCISCO — Less than half of the younger siblings of children with autism are fully immunized, according to a small study presented by Pamela E. Green in a poster session at the annual meeting of the Pediatric Academic Societies.
The study involved 34 children who were part of a prospective study of siblings of children with autism spectrum disorders. The younger children were 3 years old when Ms. Green of Bloorview MacMillan Children's Centre, Toronto, and her colleagues documented their immunization status. The older siblings with autism had a median age of 50 months (4.2 years) at that time. Data were available for 29 of the older siblings with autism spectrum disorders, and all were fully immunized.
Only 14 (41%) of the younger siblings were fully immunized. Another 5 (15%) were partially immunized, 6 (18%) had delayed immunization, and 9 (26%) had no immunizations at all.
The investigators considered a child fully immunized if there was documentation of three doses of pentavalent vaccine (diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae type b) plus a booster along with one dose of MMR. They were considered partially immunized if there were missing doses of pentavalent vaccine and/or MMR, and they were classified as delayed immunization if the MMR was not administered until 17–36 months.
The parents were questioned about what sources of information influenced their decision about immunization. Half of them said that the pediatrician was the major influence, 10% cited the Internet, 10% cited a general practitioner, and 30% cited other influences, including the media, friends, fear of autism, and their own research.
The meeting was sponsored by the American Pediatric Society, Society for Pediatric Research, Ambulatory Pediatric Association, and American Academy of Pediatrics.