Exposure to multiple vaccine antigens before 2 years of age does not appear to increase the risk for other infectious diseases between 2 and 4 years of age, according to a nested case-control study.
Concerns have been raised that early exposure to multiple vaccine antigens may cause immune dysfunction and increase the risk for non-vaccine-targeted infections. To assess that possibility, researchers evaluated data from 495,193 children across 6 integrated healthcare organizations in the United States that participate in the Vaccine Safety Datalink.
Among those, the researchers identified 47,061 who had been diagnosed in an inpatient or emergency department setting with a non-vaccine-targeted infection. They randomly selected 385 for medical review.
After excluding cases with incomplete medical records, those not coded as acute infectious illness, or those being seen for a planned procedure, the researchers ended up with a final sample of 193 children with confirmed non-vaccine-targeted infection cases diagnosed between 24 and 47 months of age. These were matched in a 1:4 manner for age, sex, and distribution of chronic diseases for a total of 751 control cases. Included children were born between January 1, 2003, and September 31, 2013, and followed through December 31, 2015.
When the researchers estimated the total number of vaccine antigens each child was exposed to between 0 and 23 months, they found no difference between the case and control groups. Specifically, the mean number of antigens was 240.6 for children with a confirmed infection and 242.9 for children without an infection.
“This study did not reveal any beneficial or detrimental associations with estimated cumulative vaccine antigen exposure in young children with non–vaccine-targeted infections in [emergency department] and inpatient settings,” write Jason M. Glanz, PhD, from Kaiser Permanente Colorado, Aurora, Colorado, and colleagues.
The researchers published the results of their study in the March 6 issue of JAMA.
“[T]he results of this large study in a US population of children offer further reassurance about the safety of the US [vaccine] schedule,” write Sean T. O’Leary, MD, MPH, from the University of Colorado Anschutz Medical Campus, and Yvonne A. Maldonado, MD, from Stanford University School of Medicine in Palo Alto, California, in an accompanying editorial.
The editorialists go on to suggest, however that although the number of antigens to which children are exposed to should be considered, immunological response to individual antigens may also play a role and will require further study.
Further, O’Leary and Maldonado posit that research confirming vaccine safety may not be enough to overcome antivaccine sentiment and suggest that improving communication between healthcare professionals and the public will also be key to improving the public’s confidence in vaccines.
“Simply providing scientific information and assuming parents will make the decision to vaccinate is not enough,” they write.
“Delivering evidence-based information to parents and clinicians in ways that inspire confidence in the robust and safe childhood immunization schedule is critical for maintaining the health of children,” O’Leary and Maldonado conclude.
The study authors acknowledge possible study limitations such as healthcare-seeking bias resulting from variable parental beliefs surrounding vaccines and vaccination schedules. In addition, they acknowledge the possibility of diagnostic bias, as physicians may be more likely to admit undervaccinated children with acute illness than children who are fully vaccinated.
Funding for this study was provided by the Centers for Disease Control and Prevention as part of the Vaccine Safety Datalink project. One study author reports receiving grants from Merck. The other study authors and editorialists have disclosed no relevant financial relationships.
JAMA. 2018;319:870-871, 906-913. Abstract, Extract
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