CINXE.COM

<!DOCTYPE html><html lang="en-US"><head><title>Just a moment...</title><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><meta name="robots" content="noindex,nofollow"><meta name="viewport" content="width=device-width,initial-scale=1"><style>*{box-sizing:border-box;margin:0;padding:0}html{line-height:1.15;-webkit-text-size-adjust:100%;color:#313131;font-family:system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,Helvetica Neue,Arial,Noto Sans,sans-serif,Apple Color Emoji,Segoe UI Emoji,Segoe UI Symbol,Noto Color Emoji}body{display:flex;flex-direction:column;height:100vh;min-height:100vh}.main-content{margin:8rem auto;max-width:60rem;padding-left:1.5rem}@media (width <= 720px){.main-content{margin-top:4rem}}.h2{font-size:1.5rem;font-weight:500;line-height:2.25rem}@media (width <= 720px){.h2{font-size:1.25rem;line-height:1.5rem}}#challenge-error-text{background-image:url(data:image/svg+xml;base64,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);background-repeat:no-repeat;background-size:contain;padding-left:34px}@media (prefers-color-scheme:dark){body{background-color:#222;color:#d9d9d9}}</style><meta http-equiv="refresh" content="390"></head><body class="no-js"><div class="main-wrapper" role="main"><div class="main-content"><noscript><div class="h2"><span id="challenge-error-text">Enable JavaScript and cookies to continue</span></div></noscript></div></div><script>(function(){window._cf_chl_opt={cvId: '3',cZone: "www.thelancet.com",cType: 'managed',cRay: '8ec482c9bd2244ba',cH: 'XFIIGZbzcA12huEODaFSJUwXCtPn8Jx9JD_QKL7XjfY-1733238913-1.2.1.1-nJnbEMzd_zT7RFsGQrxRye5QDcjKEG18GxX_O52fSEXJUS7Rb_unoHSK7l05FSdN',cUPMDTk: "\/journals\/lanonc\/article\/PIIS1470-2045(19)30404-8\/fulltext?__cf_chl_tk=9_l0c.FrmF83I8Y86DuH_Vgdj8_ldDth7sBwv7087yw-1733238913-1.0.1.1-lmLBwzKOe6FMn1A2YR7H4tVoKZJ.5je7vWB_I87VgdQ",cFPWv: 'b',cITimeS: '1733238913',cTTimeMs: '1000',cMTimeMs: '390000',cTplC: 0,cTplV: 5,cTplB: 'cf',cK: "",fa: "\/journals\/lanonc\/article\/PIIS1470-2045(19)30404-8\/fulltext?__cf_chl_f_tk=9_l0c.FrmF83I8Y86DuH_Vgdj8_ldDth7sBwv7087yw-1733238913-1.0.1.1-lmLBwzKOe6FMn1A2YR7H4tVoKZJ.5je7vWB_I87VgdQ",md: "ZcUvBPYxAH34MY2f1Ri3IMdmDrpYczYeO5LjQB2wkXQ-1733238913-1.2.1.1-nJb29JEeF5XNafd1OIS9OurFU2Gyxm.F8A4s_.4ZFw3SJ.vGQ712K.0zzAflb7KMp2bBAGelQYCWZkqC5jgSwcOgnpyE.y6FtWeijLo1ETNVdZgbMQTUq8gI87L0zyWB6zM133TtVoeTMfpQW8b1Etg6Mb9mJrDrN_Rs_k7Yi.Oer_N0RYCIUp9QMI.UYBwiquSsLXOeZfM8DzzsSR1JBm5aeQHw3SROlduG8nHJuINMbgM.lPQ_4HXA5FiNdLvaLr3kKWJZU_mIGbflbpZxk4vjmF.uSt2ihf4tWN8NXX5SxV8Q6shz6teQ0S82yNz4DGN4MQUYmB71jBAbnTi9s8sWqCuZSHi5Xh4.Tr1uSAGFi8ojK7yGQXyunT8pF2Ms706SkrlgCWhupBXgm9B0jksQ9c5N_4dtH.bEUA6YaD_jOLLjrY1TFo1cGTQT5BMzR_h2Lqcl_2Lbx5bWBTG3ON6SQFvlhtv.R2ZvtF1BUDQTH8up5RH.DL83HAvSnfdJ8xnxNxOuvboSfechdi3KFaSpPqWOaHWKuZoRXg0rFg88KyNmiW0zcz10AfDJTePZYiJK5vRdN.OKxKrnuXiwQCfn2pBG.ysd7kHk0k6me8MmAo303QLRGycLFqtiuFSAYt8ftmRMSBNwgJ412heShsDxLR3fv0fpGXyStZZP6NLYatRGXBuog679gh.W4InECwviosNQ33soBHVQUR5L.YMsub5dlnuG4VUwhbNJZ0tJhU6ck769jbuLIhnff2srNG0NHswXnHf9MOkFPREANxTPVWC1TugBJ06C0FpSd4o9wpdgwIREyqamwHEnGX36bbTaoMAJpaXTEG7kOl7VBZic3QYII7lZzv7H7uxxs64tZcdYtJZ4nFQ5uKjsRLll0kWGsOx_DKQNqjR_63PKTh_vNIx4Snfxcz79_fq7f.7.gbkm62diw9ywl8TLk1gIXWavza42yCaWEu77HUculprESAgZvK06fT0LwPtum2YWre4zddeK3tIqi5cDb0LWnRqtWj8MWQU3gIKRnh5fa3viRv0yFUs0xovjEOBANxgJVjNSiUhN0f3DwXam3spWU4lch74H0bL57Yuwk2DhPkqRs.flc5DS.g5uP_jxl0KmA2hlf4uSQeOGIZuqKn2c7KPLWQOQtiNFhYz3T6ZcXBT4T6_E_IbUjpPycjC3gO.SoaOKNn5Il7xVC.62IUtVlF7Kd.kU1PdY3wemJKtjhAexf0oDWzRD0J9BcRefLP2phkYJrb39Bt53eLflhAqXSB3TDxPHUrskmFaKBDM9myJrG.m8ApPW.STRNe11r.alYdaZDGue.bFFbYLXV7G7azRkxIhubw8zavNFekfWel6MyVHz1Nk5NMTp2VwiK8hwSKlK02nurHhtZFWbvhWaw6F4QtT7u.Ktp00kR9seELsDdqhxVQ2ag._bfheSjTHKuvnhWxX9eHgSw._AD84OuHXeensLC_hRSNhjWlVp6lqgaNN.NFn96mYJFzJnzAGhr9Hb8mXk3i_xCJmdgZPfFqENrpyuZFmfHWRd6S5zpkXTHv.rrIDdVWuqxv7V08IuLWHk10qN5Vnb.PkYDOs2algXVV2Tg84y4M23epCwi9cX4MOfi1Rm68V.bT2oz3Cblpp6Pm.t2BgbW7AszqaqNGNMVp1DDPFSb7Vw3iZ4uECockbaRkRvQpG4l9.2YiYVKAbfPobLTQtp4_yPJWkFd1.IaM2zmwheH9JX6Dz51utfRoMbuIU4ppRLiil8N0hqY4P5XXgfnBEL9xu6uAmXsnu7qgpzKYCibrATC9tPyckPmH2Q7NcTs1zZeHEmKAqnTvDTDqCRny7HnkBPF7y7h4Kxt_lfUBq4mBl7jnkK16IwbKEffo0_0bo4lSHi9R2Hk4ESKqt3bdCL8.JjGn8rRWjRN5yiy_8A.nNFBD4MDFQetamCAaoApamzVZdF7JPI4Cumo9.dpChh1yNbuswOZEAZwBnZWTTYj9drxHd9KLY_BDLk0K.ak6YP4N0XO5OQVB6pNy5FQhDorjF.n9_Rc6PIZi4HRNM_Kl904ewVU4vJBfRbTVoCp97QQIZP6cgF9TUWITHxkKyeBkWJmAABGE4i5ebxhy7i0Tt9wMQ8fUiP5O9KpTBNQgXOZzgDJi_MWihMJ_.BUxrj3cevxXow51J8t1FALbfCBEzhGUghveh9JmZg3uuvdLAwfcsxr_prbtqe_3PTkdRjX8Oc2NrrG8ircnAcITMdk3AWa1ZUjWVoUHada5AB4ICKIoNnrEKRuXXyNTIZ5bsiY7jvcS9._P_qJ.oKT.aTGmb.D19esQ6rBIjb3MBOSYGfraGK_4DzfxphCsEXQhg3rdHJxAZVc27HcgZo2W2l0EypbEuar17uHknv7HUx52MhoVs11cymfVWlgdTD3gp7mUj12OhgKC_eVY0c27D91sUvKa_FmYb5PqjOuIonXeQywHItJ6X4Tsn4Yk6e7rE01r3mVzFujmUH2ucsyVvqnDjEhDCzF3ctWl4IbTIz.AehdUNqCGmH1OsPysTSRRKvIqQk.t25N14kkSh2FRRdwdc.ENPNp4LUHdAPqS9DnXbWlgkOi98kdTmpgi9gzD6uUubzDn7KDTHKhmsCF7KfbrNVyHM8XZ1sWwtRbck53iAfw7Derl7E8XulpORowB51qIyMnCk1u7lz6jbdbwTXfj7Cs45aRR1Uf_zIBRtMhWzENcW4jV72WKxBBtt2qHa_5IecjYMfsaWxRj6p6YPamamEDgOi2tHyGCkxV1IHbFSEnaZvRYHSqvkEiLwNCRsBvJaIBVZi9WLT38r4ajXm4sP6pEkUs_hhb6aBLgpQNN1IgBnSYyezpVTGc24JuvLv98K.WTXsEcN4askma2WWLPc6rUDASI9Gmdab5DEPowGq3YgnRQmOJoHtPTtzXzvGuCLEmhI_GKWXGqxAnpTwwj4k8CMghAsHDhpMbs2G9v5XL88uImuAqQMKwplzZQwoFadPRvDPrZ_Ok13jBeJCm4qenJQ9E45xLLm5lUlkQ9YPCpyY8IQ3u68_iNGdNYP3BIgqbb62",mdrd: "tG0EQMOp6y_7.lUuOlAD.YqaZuyH7qsUXC7uw9s.Oeg-1733238913-1.2.1.1-GQR2amS1OGyYnqkGGMx66Dc85DHbzRaxKrqGCg8Is3dntzZmZAhq7oM0A4lxTExwEgGBgmebSmBWd.KhnMXQE1bZUORUpq2_zkivAJ9pCXoxWHgTR53j_ONp66nnQkOsaWLbLlx_gwkg.eTqp1sDNt.amWIIELleBX6VEMo18mXnR7pZuf6B7clAyRw_uqFWotx9p2yGFTiSPAulBYNMAgnExXttA3Ztp1p_RRMnHUdJ.824s6JayG2uhvboWt4bZuK2CoX2w3fe0M.oKImwbLkoBO4BOtZLHgIDMh5CBFHJUxc_0MI0g_P54lP1gfP_GJ9JW9nqvwW05Ng3p9nNUxGmH96pWiaG71cFi7SPl53piIwtyMq2TXaxBnOzvXr.DGX8HaOS2XSTroUNZP6xoWkTYaLk1tcqpb0kR4Dbenr5swaD8paaql5WYoiEtkKIsvRRrsg6L9y.XTFVLKIXSxHEJrP4_rdULNUKUCJO_SyI6mTkfJdz5j4VAWoFy9cA7Wj3GNz.TeJ80HpnAFQeqkO2GOuaMPUzgyKOmWFOBOx.KipXMAAX9r6GUDiOPOWNoHSnFhleHrsqBYBnnhgj87_r4SA9_BAQ5luGs4VS6IOxt84Z1S5.T1haRUjCzqmiKX7oLKHe9NuilAIzAjeWjIWdnVaSLfpGAI2IJD31C3Ow.TJdLaWMOXGhEV0YZJHE84IXTk4ZP.dUFnUxFTTP_KOQiCwhU0d338dHOW1YqGbnah08ynZDa2UOqBXNhArb5NNp5faqDIxjVddGO6WOx4UYOALSg2Yzg8BZmk6JF6GL_MkOhekF.0lxk0WQeAAmXzvaW43zzdSL5XgJ_dKZMYChOMu_v3gZNJJTd9.E31byDNpEFOJiG1Ut5c.W.YZJOuSCY6FSPXVXMdRBeEwpffOOhyr6v0yZTtzglwlLbWUCYM3FoLFcl3_Rum4DuEK43tYw0wCkhtWBayBsHSotuZRizLWFlHHlH4ekZXdYhrjmv0c.Z2RRSCopxOTwmjx01kWfy5OIU1sZ.IzaazgQf1aE5eZkOdCDdwWGO4j2wYUg0pepm66aqI9jetgMj55aa5GhmzIZ.m0RNyH8nsrmQZT7LIBhB59Rv_.mO.UK5bQbtMZ8OiXDu2Fk2U_EFD4LIS36PsSyLYJQlCAPTllrZmxzYwW_d1UxWIVNmfMftdPlXHdYiP9NMvrLWd0Ir377HJR0cKwZdySX6vi1o1KcE4ziqdhIS7sNS2Qv.YrxJoLnPaERRlb2C54xKM1P0Lo3lvf8_U1Z4HF1VtnjVcH9_dssAEl48TTrtCHF0sUIk4riZA9KOUFz2Nge1ndssYuuDEQ_GCA_xNxD0cvPBZ9CaFcrYbIaaNCElL1V9QQg_mVRWwy2kSIhDjldiWYXFVgm085VTbztHllZnO4yqrz0xRHtOP5OQwIX40PmFpotL4ZBWq6PJRckaXyGY1rSyRvWAvQZYGVPm84_Mf6JKSpfcoY4tVXjA0z6mK28Gqv0xrGO4K.TcrTkcourwhylNxMbFtPzqobA1V6InWc2f.ptW.6_OM7gJjw7OvCVZMUQ.vBL_o4CchkRn0WCeYI7s4yraWNbNYB7nBwXC_mjDA76tgpXrEzVeexOU.1QgDmC28jSIH0cDkyzLhcnGwhwiu1Ofp0niobEEVf52lbVA6bPBZJHr0tOHG9Njsvxz7a6A2loE9Hl0df2JNdx0bu2NGSaYUbUpHkTGwIZgHJCic_Aq1JerAZ3y1QzUGEjzp33zgCkSXt4KjQf1fYDBS4ldieLdrf5.swj_jy7nI7LuhRCUXnMLrdDp.6fWk_2ijlo6NtbT8WEUmQKuslUFdyuIl3EAuyFw0mrcRiCxJeO2A6ul1dVS9Gmqve8_u5JKg1hCVWBbqqArkEDSkTNERaChvNVbtnb9VAYK7daqrFQxlSAs1JhPLxORZx0GyzDwtClu.LBycY5vEKNQSLgu0ZEMgZ."};var cpo = document.createElement('script');cpo.src = '/cdn-cgi/challenge-platform/h/b/orchestrate/chl_page/v1?ray=8ec482c9bd2244ba';window._cf_chl_opt.cOgUHash = location.hash === '' && location.href.indexOf('#') !== -1 ? '#' : location.hash;window._cf_chl_opt.cOgUQuery = location.search === '' && location.href.slice(0, location.href.length - window._cf_chl_opt.cOgUHash.length).indexOf('?') !== -1 ? '?' : location.search;if (window.history && window.history.replaceState) {var ogU = location.pathname + window._cf_chl_opt.cOgUQuery + window._cf_chl_opt.cOgUHash;history.replaceState(null, null, "\/journals\/lanonc\/article\/PIIS1470-2045(19)30404-8\/fulltext?__cf_chl_rt_tk=9_l0c.FrmF83I8Y86DuH_Vgdj8_ldDth7sBwv7087yw-1733238913-1.0.1.1-lmLBwzKOe6FMn1A2YR7H4tVoKZJ.5je7vWB_I87VgdQ" + window._cf_chl_opt.cOgUHash);cpo.onload = function() {history.replaceState(null, null, ogU);}}document.getElementsByTagName('head')[0].appendChild(cpo);}());</script></body></html>