Parents not a reliable source for determining children’s vaccination status

VANCOUVER, British Columbia — Parents’ inability to recall children’s immunization history resulted in underreporting of vaccination status, significant net reporting biases and high numbers of false-negative and false-positive reports, according to a presenter at the 2010 Pediatric Academic Societies Annual Meeting.

“Parent-reported vaccination status is often used in medical settings and by certain surveillance systems. However, it has been found to be inaccurate among young children,” said Christina G. Dorell, MD, MPH, of the National Center for Immunization and Respiratory Disease. Parent-reported vaccination status among adolescents has not yet been assessed.

To assess the validity of parent-reported status of vaccination, researchers from the CDC and the U.S. Coast Guard evaluated data from the 2008 National Immunization Survey Teen (NIS-Teen) on households with adolescents aged 13-to-17 years.

NIS-Teen is conducted annually and consists of two phases.The first phase involves a random-digit-dialed household survey of parents who report the adolescents' vaccination status through recall and immunization cards or by recall only. During the second phase, the researchers contact vaccination providers to obtain the adolescents' immunization history. The NIS-Teen represents a stratified national probability sample of US households.

"Compared with provider reports, parents in the immunization card/recall group underreported adolescent vaccines with net biases ranging between -0.6 percentage points for one or more doses of the quadrivalent human papillomavirus vaccine (HPV4, Gardisil, Merck) to -25 percentage points for greater than or equal to two doses of the varicella vaccine (Var, Varivax, Merck)," Dorell said.

Parents in the recall-only group also underreported adolescent vaccine status, according to Dorell. "However, net biases were much larger for this group, ranging from 0.5 percentage points for equal to or more than three doses of HPV4 to -46 percentage points for three doses or more of the hepatitis B vaccine (HepB)."

Among the immunization card/recall group, vaccines with >20% false positive reports from parents were MMR and Tdap. Vaccines with >20% false negative reports were Var, Tdap, and MCV4. Among the recall group, vaccines with >20% false positive reports from parents were HepB, MMR, Var, Tdap. Vaccines with >20% false negative reports were HepB, MMR, Var, Tdap, MCV4 and three doses or more of HPV4.

False-positive reports indicate that parents reported receipt of the vaccines when provider records reported that they were not received. On the contrary, false-negative reports indicate that parents reported not receiving the vaccine when provider records reported that the vaccine was given. While some parents from both groups overreported receipt of some vaccines, higher false-negative rates among more vaccines and negative net biases indicate more underreporting of adolescent vaccinations among the parents in this analysis.

Parents had better reporting accuracy for vaccines administered during adolescence as opposed to those given during childhood, and net reporting biases were larger for the recall-only group compared to the immunization card/recall group. Using the immunization card improved reporting for parents; however, immunization cards with missing information may still have contributed to inaccurate parental reports.

"Medical record validation of parent-reported vaccinations is still needed for valid medical screening and surveillance of adolescent vaccination coverage. Additional strategies for improving the assessment of adolescent vaccination coverage include: using a combination of sources including recall, immunization cards, and medical records; improving vaccine provider participation in registries; reissuing immunization cards to parents and adolescents when lost; as well as encouraging parents and adolescent to bring the cards to health care visits," Dorell said. – by Melissa Foster

It is not too surprising that reports of parent about the vaccine status of children based on recall (and even when including their own records) are inaccurate, especially when they are trying to recall vaccines that were administered a long time ago. The large number of different vaccines and many abbreviations also increase the chance for mistakes. I agree with the presenters about efforts needed to increase the accuracy of immunization records. More extensive use of registries certainly would help.

– Eugene Shapiro, MD
Infectious Diseases in Children Editorial Board

For more information:

Dorell CG. #1160.8. Presented at: 2010 Pediatric Academic Societies Annual Meeting; May 1-4, 2010; Vancouver, British Columbia.

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