There is a lot of talk about claims about vaccinations increasing autism in the news lately, with a focus on MMR vaccines. I hope anyone discussing these issues is aware of the existing scientific literature investigating such potential links that have been done since the (fraudulent, retracted) work of Wakefield raised concerns about this question many years ago. For example, this excellent Danish cohort study by Anders Hviid @anders_hviid and collaborators (he does great studies, BTW) published in Annals of Internal Medicine in 2019, investigating >650k children born in Denmark between 1999 and 2010, with follow up through August 2013. They compared MMR vaccinated children with MMR unvaccinated children, using time to autism as the response and adjusting for potential confounders age, sex, birth year, other childhood vaccines, sibling history of autism, and autism risk factors. They found absolutely no evidence for increased risk of autism after MMR vaccine in the Danish children, with hazard ratio of 0.93 (95% confidence interval 0.85 to 1.02) [note, HR=1 means no difference, HR<1 means vaccinated lower risk of autism, HR>1 means vaccinated higher risk of autism]. The fact that the confidence interval contained 1 means effect was not statistically significantly less than zero, so the study cannot conclude that MMR vaccines reduce the risk of autism, but there is certainly no evidence at all or even of a suggestion they increase risk. Personally, I think it is great if scientific researchers want to do additional studies looking claims like this with rigorous, well designed studies, but they should probably look at this paper and the others in the existing literature that have been done in the past 20 years to investigate this question to identify gaps in the literature that their studies can address to best use research and financial resources to address unanswered questions. I hope people don't get the impression from any rhetoric online or in the media that this question has not been extensively studied already, because it clearly has, even if the studies did not give the results some were hoping to see. proceedings.mlr.press/v238/k…