A new study exploring the safety of aluminum in vaccines does not demonstrate a need for pediatricians to deviate from the recommended vaccine schedule, according to the AAP and others.
While the study found a possible link between aluminum in vaccines and persistent asthma in children, the AAP, Centers for Disease Control and Prevention (CDC) and the study’s authors say the study has important limitations and the findings do not prove causation.
“The overwhelming benefit of the vaccines and the long-term safety we’ve seen from them should reassure parents they should still completely vaccinate their children,” said AAP Committee on Infectious Diseases Vice Chairperson James D. Campbell, M.D., M.S., FAAP.
Dr. Campbell said he welcomed the new research. “Association Between Aluminum Exposure from Vaccines Before Age 24 Months and Persistent Asthma at Age 24-59 Months” (Daley MF, et al. Acad Pediatr., Sept. 28, 2022) was funded by CDC in response to a 2013 Institute of Medicine (now National Academy of Medicine) report calling for more research on chronic conditions after vaccination.
Researchers involved in the new study set out to look at the safety of aluminum adjuvants. Aluminum has been used in vaccines since the 1930s to improve the immune response, and previous studies have determined it is safe. It is used in numerous vaccines but is not in flu or COVID vaccines.
The observational study included data from nearly 327,000 children from seven medical care organizations. Researchers used vaccination records to calculate children’s aluminum exposure from vaccines before 2 years of age and analyzed health records to see which children had persistent asthma at 2 through 4 years of age. Persistent asthma was defined as requiring one inpatient or two outpatient asthma visits and at least two long-term asthma control medication dispenses.
The study divided children into groups with and without eczema as children with the condition are more likely to develop asthma. Researchers found average vaccine-related aluminum exposure in both groups was about 4 milligrams (mg.).
Results showed about 6% of children with eczema and 2.1% of children without eczema developed persistent asthma. Each additional milligram of vaccine-related aluminum exposure was associated with 1.3- and 1.2-times higher rates of persistent asthma among each group, respectively.
“It is theoretically possible that exposure to aluminum through vaccination could produce an immune profile biased toward Th2 and away from T helper 1 cell immune responses,” the authors wrote.
Another analysis of fully vaccinated children showed the association between vaccine-related aluminum and persistent asthma was significant only in children without eczema by 1 year of age.
The study is observational and cannot prove aluminum adjuvants cause asthma. Dr. Campbell also noted it excluded a large number of children who developed asthma before 2 years, it doesn’t take into account other risk factors for asthma and the effect size is small.
Authors also acknowledged they could not rule out possible misclassifications of aluminum exposure or persistent asthma. In addition, they did not account for different types of aluminum adjuvants.
“Considering the small effect size observed and the limitations described above, particularly related to unmeasured cofounding, these findings do not constitute strong evidence for questioning the safety of aluminum in vaccines,” authors wrote. “However, additional examination of this hypothesis appears warranted.”
The CDC said in a statement it “agrees with the authors that this single observational study has important limitations and does not show that aluminum in some childhood vaccines can cause development of persistent asthma” and it is not changing its routine childhood vaccination recommendations.
“CDC continues to strongly recommend that children stay up-to-date on routine vaccines to help children return safely to school and early care and education programs this fall,” the agency said, adding that it is exploring additional research possibilities.
The AAP encourages the additional research.
“I think (for) everyone that works in pediatric vaccines, safety is our top priority,” Dr. Campbell said. “Every study that I do, it’s the number one, primary objective, and all these observational studies, we encourage and welcome them and when safety problems have been found after vaccines have been available, then adjustments have been made.”