There have been many vit D studies before, e.g., this one with 25K participants in the USA, which found no effect: https://www.nejm.org/doi/full/10.1056/NEJMoa1

There have been many vit D studies before, e.g., this one with 25K participants in the USA, which found no effect: https://www.nejm.org/doi/full/10.1056/NEJMoa1809944 https://www.nejm.org/doi/full/10.1056/NEJMoa1809944 It's best to look at a meta analysis of all existing data/trials instead of focusing on one trial that happens to be positive.