Number of antigens in early childhood vaccines and neuropsychological outcomes at age 7-10 years

Immunization Safety Office, Division of Healthcare Quality Promotion, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA.
Pharmacoepidemiology and Drug Safety (Impact Factor: 2.94). 12/2013; 22(12). DOI: 10.1002/pds.3482
Source: PubMed


Concerns have been raised that children may be receiving too many immunizations under the recommended schedule in the USA. We used a publicly available dataset to evaluate the association between antibody-stimulating proteins and polysaccharides from early childhood vaccines and neuropsychological outcomes at age 7-10 years.
Children aged 7-10 years from four managed care organizations underwent standardized tests for domain-specific neuropsychological outcomes: general intellectual function, speech and language, verbal memory, attention and executive function, tics, achievement, visual spatial ability, and behavior regulation. Vaccination histories up to 24 months of age were obtained from medical charts, electronic records, and parents' records. Logistic regressions and structural equation modeling (SEM) were used to determine associations between total antigens up to 7, 12, and 24 months and domain-specific outcomes.
On average, children (N = 1047) received 7266, 8127, and 10 341 antigens by ages 7, 12, and 24 months, respectively. For adjusted analyses, increase (per 1000) in the number of antigens was not associated with any neuropsychological outcomes. Antigen counts above the 10th percentile, compared with lower counts, were also not associated with any adverse outcomes. However, children with higher antigen counts up to 24 months performed better on attention and executive function tests (odds ratio for lower scores = 0.51, 95% confidence interval = 0.26, 0.99). Similar results were found with SEM analysis (b = 0.08, p = 0.02).
We did not find any adverse associations between antigens received through vaccines in the first two years of life and neuropsychological outcomes in later childhood. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

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    ABSTRACT: While the large majority of parents in the U.S. vaccinate their children according to the recommended immunization schedule, some parents have refused or delayed vaccinating, often citing safety concerns. In response to public concern, the U.S. Institute of Medicine (IOM) evaluated existing research regarding the safety of the recommended immunization schedule. The IOM concluded that although available evidence strongly supported the safety of the currently recommended schedule as a whole, additional observational research was warranted to compare health outcomes between fully vaccinated children and those on a delayed or alternative schedule. In addition, the IOM identified the Vaccine Safety Datalink (VSD) as an important resource for conducting this research. Guided by the IOM findings, the Centers for Disease Control and Prevention (CDC) commissioned a White Paper to assess how the VSD could be used to study the safety of the childhood immunization schedule. Guided by subject matter expert engagement, the resulting White Paper outlines a 4 stage approach for identifying exposure groups of undervaccinated children, presents a list of health outcomes of highest priority to examine in this context, and describes various study designs and statistical methods that could be used to analyze the safety of the schedule. While it appears feasible to study the safety of the recommended immunization schedule in settings such as the VSD, these studies will be inherently complex, and as with all observational studies, will need to carefully address issues of confounding and bias. In light of these considerations, decisions about conducting studies of the safety of the schedule will also need to assess epidemiological evidence of potential adverse events that could be related to the schedule, the biological plausibility of an association between an adverse event and the schedule, and public concern about the safety of the schedule.
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