Danish Study Affirms Safety of Aluminum in Childhood Vaccines

A nationwide analysis in Denmark found no association between cumulative aluminum exposure in pediatric vaccines and the incidence of chronic diseases. The findings, published in the Annals of Internal Medicine, offer further data on the safety of vaccines as vaccine skepticism spreads in the United States.¹

Doctor holding syringe to vaccinate baby | Image Credit: © sonar512 - stock.adobe.com

"Our results, based on 1.2 million Danish children and a study period covering 24 years, provide robust evidence supporting the safety of childhood vaccines," Anders Hviid, MSc, DrMedSci, co-author from Statens Serum Institut, told MedPage Today. "This is evidence that parents, clinicians, and public health officials need to make the best choices for the health of our children."²

Aluminum-containing adjuvants are frequently incorporated into non-live vaccines to strengthen the immune response by attaching to vaccine antigens. These adjuvants are found in several routine childhood immunizations, including those for diphtheria, tetanus, and pertussis; Haemophilus influenzae type b (Hib); pneumococcal conjugate (PCV); and hepatitis A and B.¹

The Danish study comes amidst concerns over the safety of aluminum-containing adjuvants in vaccines. Since his installment as secretary of the Department of Health and Human Services, Robert F. Kennedy Jr. (RFK) continues to question the safety of vaccines. The potential clinical consequences of aluminum follow other concerns about vaccine safety, including—but not limited to—thimerosal. In fact, according to The Guardian, RFK recently announced that vaccine manufacturers are required to remove thimerosal from vaccines, despite decades of research showing no evidence of adverse health effects.²

“This work was motivated by ongoing concerns about potential harms of aluminum-adsorbed nonlive vaccines,” the authors wrote.¹

In the cohort study, investigators assessed the association between cumulative aluminum exposure from early childhood vaccination and risk for autoimmune, atopic or allergic, and neurodevelopmental disorders using registry data from children born in Denmark between 1997 and 2018 who were alive and residing in the country at 2 years of age.¹

The analysis included a total of 1,224,176 children who received a cumulative aluminum amount per 1-mg increase through vaccination during the first 2 years of life. The investigators focused on the incidence of 50 chronic disorders, including autoimmune (dermatologic, endocrinologic, hematologic, gastrointestinal, and rheumatic), atopic or allergic (asthma, atopic dermatitis, rhinoconjunctivitis, and allergy), and neurodevelopmental (autism spectrum disorder and attention deficit–hyperactivity disorder).¹

According to the data, no link was found between cumulative aluminum exposure from vaccines in the first 2 years of life and an increased risk across any of the 50 health conditions examined. When outcomes were grouped, each 1-mg increase in aluminum exposure was associated with an adjusted hazard ratio of 0.98 (95% CI, 0.94–1.02) for autoimmune disorders, 0.99 (95% CI, 0.98–1.01) for atopic or allergic conditions, and 0.93 (95% CI, 0.90–0.97) for neurodevelopmental disorders. For most individual conditions, the upper limits of the 95% confidence intervals did not support relative risk increases exceeding 10% to 30%.¹

“In conclusion…in this nationwide cohort study of approximately 1.2 million children, findings were incompatible with moderate to large relative increases in the risks for autoimmune, atopic or allergic, and neurodevelopmental disorders associated with early childhood exposure to aluminum-adsorbed vaccines for most outcomes, although small relative increases could not be statistically excluded, particularly for some rarer outcomes,” the authors said.¹

REFERENCES

1. Andersson N, Svalgaard I, Hoaffmann S, et al. Aluminum-adsorbed vaccines and chronic diseases in childhood: A nationwide cohort study. Annals of Internal Medicine. July 15, 2025. Doi:10.7326/ANNALS-25-00997

2. George J. Aluminum in vaccines not culprit in kids' chronic diseases, study shows. MedPage Today. July 14, 2025. Accessed July 23, 2025. https://www.medpagetoday.com/neurology/autism/116499?xid=nl_mpt_morningbreak2025-07-15&mh=6d2b5f4f91352444bdf817a9c17750bc&zdee=gAAAAABm4uL9FCoIf1N83nrcwYYqnQUvN6Iw4dbaY-dGva4sOp57nSM2Ew3wD87ohRuoseQBDbCp1MG30J6ETpHXK1wNpp0NgnGTMFXrtFaNfWUoL5ekf-Y%3D&utm_source=Sailthru&utm_medium=email&utm_campaign=MorningBreak_071525&utm_term=NL_Gen_Int_Daily_News_Update_active

3. RFK Jr to remove preservative thimerosal from all US vaccines. The Guardian. July 23, 2025. Accessed July 23, 2024. https://www.theguardian.com/us-news/2025/jul/23/rfk-jr-thimerosal-vaccines