HONOLULU — Children adopted internationally by American parents often are accompanied by immunization records from their birth countries, but the records cannot be relied on, according to a study of more than 400 children. It's important to inform adoptive parents of this, Emaculate Verla-Tebit, Ph.D., of Case Western Reserve University, Cleveland, said in an interview. Parents then can decide whether to simply revaccinate or to order serum antibody testing and vaccinate based on those results.
The cross-sectional study involved 465 children seen at an adoption health clinic at Rainbow Babies and Children's Hospital in Cleveland. The investigators excluded children who had hepatitis B or C infections, those who presented more than 180 days after their arrival into the United States, and those who had received any vaccine in the United States.
The children came from Russia, China, Guatemala, Eastern Europe, Southeast Asia, the West Pacific, and Latin America; they were a mean 19.4 months at adoption. More than 85% had vaccine records available. The investigators obtained venous blood samples and measured antibody titers for diphtheria, tetanus, measles, hepatitis B, and polio.
The level of protective immunity was worst for polio. Of children reported to have received three or more polio vaccine doses, only about 60% had protective immunity to polio type 1, 85% had protective immunity to type 2, and just over 50% had protective immunity to type 3, Dr. Verla-Tebit reported in a poster presented at the annual meeting of the Pediatric Academic Societies.
Of children reported to have received two or more doses of hepatitis B vaccine, 95% had protective immunity. Of children reported to have received one or more doses of measles vaccine, about 80% had protective immunity.
Of children reported to have three or more doses of diphtheria vaccine, 95% had protective immunity, and of those who were reported to have three or more doses of tetanus vaccine, 90% had protective immunity.
Dr. Verla-Tebit said that several factors could explain the discordance between immunization records and protective immunity. It's possible that some records were falsified, but it's also possible that in some cases there may have been a break in the cold chain—a common occurrence in developing countries—which could have compromised vaccine strength.
Another possibility is that the child's nutritional status may have played a role. Investigators judged 79% of children in this study to be well nourished, 15% to have moderate to severe chronic malnutrition, and 6% to have moderate to severe acute malnutrition.
Dr. Verla-Tebit stated that she had no conflicts of interest related to her study.