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Assessing misclassification of vaccination status: Implications for studies of the safety of the childhood immunization schedule
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4 04 2017
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Source: Vaccine. 35(15):1873-1878
[PDF-81.32 KB]
Details:
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Alternative Title:Vaccine
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Personal Author:
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Description:Background:
To address public concern about the safety of the childhood immunization schedule, the Institute of Medicine recommended observational studies comparing adverse health outcomes of fully vaccinated children to children under-vaccinated due to parental choice. Misclassification of vaccination status could bias such studies.
Objective:
To assess risk of misclassification of vaccination status within the Vaccine Safety Datalink (VSD).
Design/methods:
A retrospective cohort study was conducted in three phases. In phase 1, electronic health record (EHR) data were used to identify patterns of under-vaccination during the first 24 months of life potentially due to parental choice. In phase 2, a random sample of records of under-vaccinated children was manually reviewed. In phase 3, a separate sample of parents were surveyed to assess whether EHR data accurately reflected their child’s vaccination status. Phases 1 and 2 were conducted at 6 VSD sites, phase 3 at 1 site.
Results:
The study cohort included 361,901 children born 2004 through 2012. By 24 months of age, 198,249 (54.8%) were fully vaccinated with no delays, 84,698 (23.4%) experienced delays but were fully vaccinated by 24 months of age, 4865 (1.3%) received no vaccines, 3789 (1.0%) delayed starting vaccination until ≤4 months of age, 4781 (1.3%) had consistent vaccine-limiting (≤2 vaccines per visit), and the remaining 65,519 (18.1%) were missing vaccine series or doses. When a diagnosis code for vaccine refusal was present in EHR data, encounter notes confirmed vaccine refusal as the reason for under-vaccination for nearly 100% of sampled records. Parent surveys confirmed these findings. Parents of under-vaccinated children were more likely to report visiting an alternative medical provider than parents of fully vaccinated children.
Conclusions:
Specific groups of children, under-vaccinated due to parental choice, can be identified with relatively low likelihood of misclassification of vaccination status using EHR-based vaccine data and diagnosis codes.
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Source:
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Pubmed ID:28285983
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Pubmed Central ID:PMC6445250
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Funding:
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Volume:35
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Issue:15
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