On November 27, 2025, the World Health Organization’s Global Advisory Committee on Vaccine Safety (GACVS) reviewed two newly conducted systematic literature reviews examining potential links between vaccination and autism spectrum disorder (ASD).

After carefully evaluating published studies from January 2010 through August 2025, the Committee upheld its earlier findings from reviews in 2002, 2004, and 2012, confirming that there is no credible evidence that vaccines cause ASD.

In vaccine safety research, a potential causal relationship is considered when high-quality studies consistently show a statistical link between a vaccine and an outcome. Systematic reviews use comprehensive database searches and evaluate the quality of each study. The most reliable conclusions are drawn from well-designed studies with minimal bias, while those with flaws or high bias carry less weight.

The first review analyzed studies concerning thiomersal-containing vaccines and ASD, as well as overall vaccine exposure and ASD. This updated a previous review from 2012 and included English-language papers published from 2010 to August 2025. A total of 31 studies were assessed—16 related to thiomersal and ASD, 15 examining general vaccine exposure. Five meta-analyses were also reviewed, including work covering research prior to 2010.

Out of the 31 individual studies from 11 countries, 20—along with all five meta-analyses—found no evidence linking vaccines (including those with thiomersal) to ASD. The remaining 11 studies, many from a single research group in the United States, suggested a possible link but were significantly limited by weak methodology and a high risk of bias. Taken together, the substantial and high-quality body of global research continues to confirm the safety of vaccines used during childhood and pregnancy, with no proven link to ASD. A comprehensive draft of the review’s findings has been compiled.

The second systematic review explored the health effects of vaccines containing aluminium-based adjuvants. It analyzed data from multiple literature sources up to March 2023. Ten randomized controlled trials and seven large cohort studies showed no link between these vaccines and the development of chronic or systemic illnesses. Although two ecological studies reported a possible correlation between aluminium exposure from vaccines and ASD prevalence, these studies lacked the ability to establish causation and had serious methodological weaknesses. Therefore, their findings were deemed to have very low evidential value.

Additionally, the Committee examined a more recent study not included in the above review. This large-scale cohort study analyzed national registry data from children born in Denmark between 1997 and 2018. Using rigorous methods, researchers found no association between early exposure to aluminium-containing vaccines and the occurrence of 50 chronic or developmental conditions, including ASD. This further supports the safety of vaccines that use aluminium in small quantities.

Following this latest assessment, GACVS repeats its conclusions from the past reviews in 2002, 2004, and 2012: current scientific evidence of high quality clearly demonstrates that vaccines—whether they contain thiomersal, aluminium, or both—do not cause autism.

[1] Report of Global Advisory Committee on Vaccine Safety, World Health Organization. 2002

[2] MMR and autism, World Health Organization. 2003

[3] Weekly Epidemiological Record, World Health Organization. 2005

[4] Weekly Epidemiological Record, World Health Organization. 2012

[5] Andersson NW, Bech Svalgaard I, Hoffmann SS, Hviid A. Aluminum-Adsorbed Vaccines and Chronic Diseases in Childhood: A Nationwide Cohort Study. Ann Intern Med. 2025; 178:1369-1377.