Covid-19: Validity of key studies in doubt after leading journals issue expressions of concern

Doubts have emerged about the validity of widely cited research papers that have informed global health policy during the covid-19 pandemic. On 2 June the Lancet issued an expression of concern1 relating to a study2 it published on 22 May suggesting that hospital patients with covid-19 being treated with hydroxychloroquine and chloroquine were at increased risk of dying and of ventricular arrhythmia than patients who did not receive the drugs....