Correlates of protection against symptomatic and asymptomatic SARS-CoV-2 infection
Shuo Feng, Daniel J. Phillips, Thomas White, Homesh Sayal, Parvinder K. Aley, Sagida Bibi, Christina Dold, Michelle Fuskova, Sarah C. Gilbert, Ian Hirsch, Holly E. Humphries, Brett Jepson, Elizabeth J. Kelly, Emma Plested, Kathryn Shoemaker, Kelly Thomas, Johan Vekemans, Tonya Villafana, Teresa Lambe, Andrew J. Pollard, Merryn Voysey, the Oxford COVID Vaccine Trial Group, Syed Adlou, Lauren Allen, Brian Angus, Rachel Anslow, Marie‐Claude Asselin, Natalie Baker, Philip Baker, Thomas Barlow, Amy Beveridge, Kevin R. Bewley, Phillip J. Brown, Emily Brunt, Karen R. Buttigieg, Susana Camara, Sue Charlton, Emily Chiplin, Paola Cicconi, Elizabeth Clutterbuck, Andrea M. Collins, Naomi S. Coombes, Sue Ann Costa Clemens, M. Davison, Tesfaye Demissie, Tanya Dinesh, Alexander D. Douglas, C.J. Duncan, Katherine R. W. Emary, Katie Ewer, Sally Felle, Daniela M. Ferreira, Adam Finn, Pedro M. Folegatti, Ross Fothergill, Sara Fraser, Harriet Garlant, Laura Gatcombe, Kerry Godwin, Anna L. Goodman, Christopher Green, Bassam Hallis, Thomas C. Hart, Paul T. Heath, Helen Hill, Adrian V. S. Hill, Daniel Jenkin, Mwila Kasanyinga, Simon Kerridge, Chanice Knight, Stephanie Leung, Vincenzo Libri, Patrick Lillie, Spyridoula Marinou, Joanna McGlashan, Alastair McGregor, Lorna McInroy, Angela M. Minassian, Yama F Mujadidi, Elizabeth J. Penn, Christos J. Petropoulos, Katrina M. Pollock, Pamela C. Proud, Samuel Provstgaard-Morys, Durga Rajapaska, Maheshi Ramasamy, Katherine Sanders, Imam H. Shaik, Nisha Singh, Andrew Smith, Matthew D. Snape, Rinn Song, Sonu Shrestha, Rebecca Sutherland, Emma C. Thomson, David P. J. Turner, Alice Webb-Bridges, Terri Wrin, Christopher J. Williams
Abstract
Abstract The global supply of COVID-19 vaccines remains limited. An understanding of the immune response that is predictive of protection could facilitate rapid licensure of new vaccines. Data from a randomized efficacy trial of the ChAdOx1 nCoV-19 (AZD1222) vaccine in the United Kingdom was analyzed to determine the antibody levels associated with protection against SARS-CoV-2. Binding and neutralizing antibodies at 28 days after the second dose were measured in infected and noninfected vaccine recipients. Higher levels of all immune markers were correlated with a reduced risk of symptomatic infection. A vaccine efficacy of 80% against symptomatic infection with majority Alpha (B.1.1.7) variant of SARS-CoV-2 was achieved with 264 (95% CI: 108, 806) binding antibody units (BAU)/ml: and 506 (95% CI: 135, not computed (beyond data range) (NC)) BAU/ml for anti-spike and anti-RBD antibodies, and 26 (95% CI: NC, NC) international unit (IU)/ml and 247 (95% CI: 101, NC) normalized neutralization titers (NF 50 ) for pseudovirus and live-virus neutralization, respectively. Immune markers were not correlated with asymptomatic infections at the 5% significance level. These data can be used to bridge to new populations using validated assays, and allow extrapolation of efficacy estimates to new COVID-19 vaccines.