A 24-year nationwide study of more than 1.2 million Danish children has found no evidence that aluminum salts used as adjuvants in childhood vaccines raise the risk of chronic illnesses such as autism, asthma, allergies or autoimmune diseases. The research, led by epidemiologist Anders Hviid of Denmark’s Statens Serum Institut and published in the Annals of Internal Medicine, is the largest assessment to date of vaccine-related aluminum safety. Using Denmark’s comprehensive health registries, the authors calculated each child’s cumulative aluminum exposure from routine vaccinations during the first two years of life and tracked diagnoses for 50 chronic conditions through at least age five. For every additional milligram of aluminum received, the adjusted hazard ratios were 0.98 for any autoimmune disorder, 0.99 for any allergic or atopic disorder, and 0.93 for neurodevelopmental disorders, indicating no increased risk and, in some cases, a slightly lower incidence. No dose-response pattern emerged even as vaccine schedules — and aluminum content — changed over the 1997-2018 birth cohorts. The findings counter claims by vaccine-skeptic groups that aluminum adjuvants are harmful. Independent experts, including Johns Hopkins professor Anna Durbin and retired Marshfield Clinic researcher Edward Belongia, called the work the most definitive observational analysis yet on the question. The study also addresses concerns raised by a smaller 2023 U.S. report that had suggested a possible link between aluminum exposure and childhood asthma. The authors note that while their registry design cannot rule out very rare effects, the data exclude any moderate or large risk increases and support continued use of aluminum-containing vaccines, which have no ready substitutes. With vaccine hesitancy still hampering immunisation rates in several countries, public-health officials say the Danish results provide strong reassurance about a cornerstone of global childhood vaccination programmes.