Technical note Open Access
Updated 31 July, 2020. This is a letter to the editor about a publication in Nature by the UK OpenSAFELY Collaborative, available at https://www.nature.com/articles/s41586-020-2521-4. This work has been submitted to Nature in the category "Matters Arising."
Earlier versions of this letter (see versions) were in response to the pre-print of the Nature paper, available at https://www.medrxiv.org/content/10.1101/2020.05.06.20092999v1.full.pdf.