Correlates of protection against symptomatic and asymptomatic SARS-CoV-2 infection
Feng S., Phillips DJ., White T., Sayal H., Aley PK., Bibi S., Dold C., Fuskova M., Gilbert SC., Hirsch I., Humphries HE., Jepson B., Kelly EJ., Plested E., Shoemaker K., Thomas KM., Vekemans J., Villafana TL., Lambe T., Pollard AJ., Voysey M., Adlou S., Allen L., Angus B., Anslow R., Asselin M-C., Baker N., Baker P., Barlow T., Beveridge A., Bewley KR., Brown P., Brunt E., Buttigieg KR., Camara S., Charlton S., Chiplin E., Cicconi P., Clutterbuck EA., Collins AM., Coombes NS., Clemens SAC., Davison M., Demissie T., Dinesh T., Douglas AD., Duncan CJA., Emary KRW., Ewer KJ., Felle S., Ferreira DM., Finn A., Folegatti PM., Fothergill R., Fraser S., Garlant H., Gatcombe L., Godwin KJ., Goodman AL., Green CA., Hallis B., Hart TC., Heath PT., Hill H., Hill AVS., Jenkin D., Kasanyinga M., Kerridge S., Knight C., Leung S., Libri V., Lillie PJ., Marinou S., McGlashan J., McGregor AC., McInroy L., Minassian AM., Mujadidi YF., Penn EJ., Petropoulos CJ., Pollock KM., Proud PC., Provstgaard-Morys S., Rajapaska D., Ramasamy MN., Sanders K., Shaik I., Singh N., Smith A., Snape MD., Song R., Shrestha S., Sutherland RK., Thomson EC., Turner DPJ., Webb-Bridges A., Wrin T., Williams CJ.
AbstractThe 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 (NF50) 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.