Largest Study Ever Conducted Rules Out Link Between Aluminum In Vaccines And Autism Or ADHD

Childhood vaccines use aluminum to boost the immune system's response, but many fear it causes autism, allergies, or autoimmune diseases. A new study of more than 1.2 million children in Denmark showed that there is no increased risk of these diseases related to the amount of aluminum received in vaccines. In other words, vaccines containing aluminum are safe, even when used from the earliest years of life.

For many years, concerns have circulated, especially on social media and among anti-vaccine groups, that the aluminum used in childhood vaccines could cause problems such as autism, autoimmune diseases, or allergies.

Many childhood vaccines, such as those against hepatitis B, tetanus, diphtheria, whooping cough, and pneumococcus, use a substance called aluminum as an adjuvant. This component is not the "active ingredient" of the vaccine, but rather a booster that helps the body generate a stronger and longer-lasting immune response to the antigen.

The use of aluminum-based adjuvants has existed for many decades, and these vaccines are part of national childhood vaccination programs in several countries, including Brazil and Denmark.

However, despite its long history and approval by health agencies around the world, concerns persist among some people about the possible side effects of aluminum, especially on children's neurological and immunological development.

These concerns stem primarily from older animal studies or limited analyses in humans, often with little solid scientific basis. Some of these studies have suggested that the aluminum present in vaccines could be linked to autoimmune problems, allergic diseases, or even neurodevelopmental disorders such as autism or ADHD (attention deficit hyperactivity disorder).

This has generated fear and misinformation, fueling conspiracy theories about vaccines. However, the human data that actually supports these risks are fragile and inconclusive; they are generally small, observational studies that lack the necessary rigor to draw reliable conclusions.

What has been missing until now is a comprehensive, large-scale analysis with real-world vaccination and health data over time.

That's exactly what Danish researchers did in this new study, one of the most robust ever conducted on the subject. Taking advantage of a unique feature of the Danish healthcare system, which maintains detailed national records on vaccinations, medical diagnoses, and health history for the entire population, the scientists studied more than 1.2 million children born between 1997 and 2018, followed until 2020.

Because the country's childhood vaccination program has undergone changes over the years, with vaccine replacements and formulation changes, the amount of aluminum children received naturally varied between generations.

During the study, the scientists calculated the cumulative amount of aluminum each child received through vaccinations up to the age of two. They then investigated whether there was any relationship between this exposure and the future risk of developing 50 different chronic diseases.

These included autoimmune conditions (such as lupus, type 1 diabetes, thyroid disease, and rheumatic diseases), allergic or atopic conditions (such as asthma, atopic dermatitis, allergic rhinitis, and food allergies), and neurodevelopmental disorders such as autism and ADHD.

The result was very clear: there was no association between the amount of aluminum received in vaccines and the risk of developing any of these diseases. In other words, even as the aluminum dose increased, the risk did not increase. In fact, the numbers indicated a slight downward trend, especially for neurodevelopmental disorders, although this decrease was not considered clinically significant.

The adjusted hazard ratio was 0.98 for autoimmune diseases, 0.99 for allergic diseases, and 0.93 for neurodevelopmental disorders, values that indicate no increased risk.

Furthermore, for most diseases, the confidence intervals excluded even moderate increases (e.g., 10% or 30%) in risk, which further strengthens the result.

One of the study's strengths is that it used real, high-quality data from an entire population, with follow-up for over 20 years. It is also important to highlight that the dynamics of vaccines over time generated variations in aluminum content without this being affected by parental decisions or socioeconomic characteristics, one of the reasons why the results are considered reliable.

The main limitation is that individual medical records were not manually reviewed; diagnoses were obtained from electronic records. Even so, these records are recognized for their high quality and routine use in epidemiological research.

The overall conclusion of the study is reassuring: there is no evidence that aluminum-containing vaccines cause autism, autoimmune diseases, or allergies.

This work represents a strong counterpoint to claims that aluminum in vaccines is dangerous. It shows, based on solid data and a very large population, that these vaccines remain safe and essential for protecting children.

While the study cannot rule out very small effects (particularly for very rare diseases), it confidently rules out any significant risk that would justify widespread concern. It is, therefore, an important scientific response to a myth that has been perpetuated for decades and has never had a concrete basis.

READ MORE:

Aluminum-Adsorbed Vaccines and Chronic Diseases in Childhood: A Nationwide Cohort Study

Niklas Worm Andersson, Ingrid Bech Svalgaard, Stine Skovbo Hoffmann, and Anders Hviid

Annals of Internal Medicine. Epub 15 July 2025. 

doi:10.7326/ANNALS-25-00997

Abstract: 

Aluminum is used as an adjuvant in nonlive vaccines administered in early childhood. Concerns persist about potential associations between vaccination with aluminum-adsorbed vaccines and increased risk for chronic autoimmunity, atopy or allergy, and neurodevelopmental disorders. Large-scale safety data remain limited. To assess the association between cumulative aluminum exposure from early childhood vaccination and risk for autoimmune, atopic or allergic, and neurodevelopmental disorders. A cohort study linking nationwide registry data on childhood vaccinations, outcome diagnoses, and potential confounders, leveraging the variations in the aluminum content of childhood vaccines over time. Denmark, 1997 to 2020. 1 224 176 children born in Denmark between 1997 and 2018 who were alive and residing in the country at age 2 years. Cumulative aluminum amount received (per 1-mg increase) through vaccination during the first 2 years of life. Incident events 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). Cumulative aluminum exposure from vaccination during the first 2 years of life was not associated with increased rates of any of the 50 disorders assessed. For groups of combined outcomes, adjusted hazard ratios per 1-mg increase in aluminum exposure were 0.98 (95% CI, 0.94 to 1.02) for any autoimmune disorder, 0.99 (CI, 0.98 to 1.01) for any atopic or allergic disorder, and 0.93 (CI, 0.90 to 0.97) for any neurodevelopmental disorder. For most individually analyzed outcomes, the upper bounds of the 95% CIs were incompatible with relative increases greater than 10% or 30%. Individual medical records were not reviewed. This nationwide cohort study did not find evidence supporting an increased risk for autoimmune, atopic or allergic, or neurodevelopmental disorders associated with early childhood exposure to aluminum-adsorbed vaccines. For most outcomes, the findings were inconsistent with moderate to large relative increases in risk, although small relative effects, particularly for some rarer disorders, could not be statistically excluded.