Ahmed HU et al. Lancet 2017; 389(10071): 815-822. doi:10.1016/S0140-6736(16)32401-1 Please follow the link below to view this article in full on a third party website. Note that a subscription or payment may be required. http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(16)32401-1/