Cited by 1,163SARS-CoV-2 and COVID-19 ResearchCOVID-19 Clinical Research StudiesAnimal Virus Infections Studies

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Correlates of protection against symptomatic and asymptomatic SARS-CoV-2 infection

Open access
Feng, Shuo, Phillips, Daniel J., White, Thomas, Sayal, Homesh, Aley, Parvinder K., Bibi, Sagida, Dold, Christina, Fuskova, Michelle, Gilbert, Sarah C., Hirsch, Ian, Humphries, Holly E., Jepson, Brett, Kelly, Elizabeth J., Plested, Emma, Shoemaker, Kathryn, Thomas, Kelly M., Vekemans, Johan, Villafana, Tonya L., Lambe, Teresa, Pollard, Andrew J., Voysey, Merryn, the Oxford COVID Vaccine Trial Group, Adlou, Syed, Allen, Lauren, Angus, Brian, Anslow, Rachel, Asselin, Marie-Claude, Baker, Natalie, Baker, Philip, Barlow, Thomas, Beveridge, Amy, Bewley, Kevin R., Brown, Phillip, Brunt, Emily, Buttigieg, Karen R., Camara, Susana, Charlton, Sue, Chiplin, Emily, Cicconi, Paola, Clutterbuck, Elizabeth A., Collins, Andrea M., Coombes, Naomi S., Clemens, Sue Ann Costa, Davison, Melanie, Demissie, Tesfaye, Dinesh, Tanya, Douglas, Alexander D., Duncan, Christopher J. A., Emary, Katherine R. W., Ewer, Katie J., Felle, Sally, Ferreira, Daniela M., Finn, Adam, Folegatti, Pedro M., Fothergill, Ross, Fraser, Sara, Garlant, Harriet, Gatcombe, Laura, Godwin, Kerry J., Goodman, Anna L., Green, Christopher A., Hallis, Bassam, Hart, Thomas C., Heath, Paul T., Hill, Helen, Hill, Adrian V. S., Jenkin, Daniel, Kasanyinga, Mwila, Kerridge, Simon, Knight, Chanice, Leung, Stephanie, Libri, Vincenzo, Lillie, Patrick J., Marinou, Spyridoula, McGlashan, Joanna, McGregor, Alastair C., McInroy, Lorna, Minassian, Angela M., Mujadidi, Yama F., Penn, Elizabeth J., Petropoulos, Christos J., Pollock, Katrina M., Proud, Pamela C., Provstgaard-Morys, Samuel, Rajapaska, Durga, Ramasamy, Maheshi N., Sanders, Katherine, Shaik, Imam, Singh, Nisha, Smith, Andrew, Snape, Matthew D., Song, Rinn, Shrestha, Sonu, Sutherland, Rebecca K., Thomson, Emma C., Turner, David P. J., Webb-Bridges, Alice, Wrin, Terri, Williams, Christopher J.·2021·Nature Medicine

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.

Overview

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Written from the paper’s full text.

TL;DR

In the UK COV002 trial, higher anti-spike IgG, anti-RBD IgG, pseudovirus neutralizing, and live-virus neutralizing antibody levels at 28 days after a second ChAdOx1 nCoV-19 dose were associated with lower risk of symptomatic COVID-19, but not asymptomatic infection. Antibody values corresponding to 80% vaccine efficacy against primary symptomatic COVID-19 were 264 BAU/ml for anti-spike IgG, 506 BAU/ml for anti-RBD IgG, 26 IU/ml for pseudovirus neutralization, and 247 NF50 for live-virus neutralization.

Key findings

  • Among 4,372 participants in the correlates population, there were 174 breakthrough NAAT+ SARS-CoV-2 infections; correlates analysis included 171 cases and 1,404 noncases with at least one assay readout. Risk of symptomatic COVID-19 decreased with increasing anti-spike IgG (P = 0.003), anti-RBD IgG (P = 0.018), pseudovirus neutralization titer (P = 0.005), and live-virus neutralization titer (P < 0.001).
  • The antibody level associated with 80% VE against primary symptomatic COVID-19 was 40,923 AU/ml anti-spike IgG, equivalent to 264 BAU/ml (95% CI: 108, 806); 506 BAU/ml anti-RBD IgG (95% CI: 135, NC); 26 IU/ml pseudovirus neutralization (95% CI: NC, NC); and 247 NF50 live-virus neutralization (95% CI: 101, NC).
  • No significant associations were found between any assay and protection against asymptomatic infection, including in sensitivity analysis restricting to high viral load (all P > 0.05).
  • For symptomatic cases with shortness of breath, 80% VE was achieved at lower immune marker levels than for symptomatic cases in general; no significant associations were observed for symptomatic cases without shortness of breath (all P > 0.05).

Methods

  • Data came from COV002, a phase 2/3 randomized single-blind vaccine efficacy trial across 19 UK sites; participants were randomized to ChAdOx1 nCoV-19 or MenACWY control. The correlates population included baseline SARS-CoV-2 N-protein-seronegative participants with a PB28 visit within 14–42 days after the second dose and follow-up to at least 7 days after PB28; the correlates cohort comprised those with biomarker data.
  • Immune markers measured at PB28 were anti-spike IgG, anti-RBD IgG, pseudovirus neutralization, and live-virus neutralization, converted to WHO international standard units. Outcomes were primary symptomatic COVID-19 (NAAT+ with at least one qualifying symptom) and asymptomatic infection (NAAT+ on weekly self-swab with no symptoms).
  • Log-transformed immune markers were analyzed with generalized additive models for binary outcomes using cubic spline smooths, adjusted for baseline exposure risk and weighted by inverse probability weights for sample availability. Correlates of VE were derived by comparing predicted absolute risk with the MenACWY control population risk; 95% CIs used 10,000 bootstrap samples.

Limitations

  • Stated: analyses were based on a mainly white UK population with cases mostly due to B.1.177 and B.1.1.7 variants, so modeled relationships may not apply where other variants dominate or different neutralization strains are used. Many analyses were conducted and P values are unadjusted for multiple comparisons. Results apply to two doses of ChAdOx1 nCoV-19 and may not apply to a single dose or other COVID-19 vaccines. Age profile was not explored due to few older adults; T cells and humoral–cellular interactions were not evaluated; mechanistic versus nonmechanistic correlates could not be determined. No vaccinated participants were hospitalized, so correlates against severe disease or hospitalization could not be assessed. Wide CIs around estimates should be noted, and no single threshold indicated sterilizing immunity.
  • Evident from the text: the correlates relate to protection against mild disease, defined as NAAT+ with at least one symptom, during the subsequent 4- to 6-month period, and represent antibody levels at 28 days after a second dose rather than at the time of exposure.

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Crossref · 10.1038/s41591-021-01540-1

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Figures

Fig. 1 Predicted absolute risk of primary symptomatic COVID-19 as a function of immune markers measured at PB28 by generalized additive regression. a–d, Predicted absolute risk of primary symptomatic COVID-19 as a function of anti-spike IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis) (a), anti-RBD IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis) (b), pseudovirus neutralization antibody titers at PB28 (47 cases, 828 noncases included in the analysis (c), and live-virus neutralization antibody titers PB28 (36 cases, 412 noncases included in the analysis) (d). Gray horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the CI around the predicted mean probability (green line).
Fig. 1 Predicted absolute risk of primary symptomatic COVID-19 as a function of immune markers measured at PB28 by generalized additive regression. a–d, Predicted absolute risk of primary symptomatic COVID-19 as a function of anti-spike IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis) (a), anti-RBD IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis) (b), pseudovirus neutralization antibody titers at PB28 (47 cases, 828 noncases included in the analysis (c), and live-virus neutralization antibody titers PB28 (36 cases, 412 noncases included in the analysis) (d). Gray horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the CI around the predicted mean probability (green line).CC BY · PubMed Central
Fig. 2 Relative risk of primary symptomatic COVID-19 among vaccine recipients compared with MenACWY control arm participants as a function of immune markers measured at PB28. a, Anti-spike IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). b, Anti-RBD IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). c, Pseudovirus neutralization antibody titers at PB28 (47 cases, 828 noncases included in the analysis). d, Live-virus neutralization antibody titers at PB28 (36 cases, 412 noncases included in the analysis). Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared with that of the MenACWY control arm participants, derived by dividing the output curve from Fig. 1 by the overall risk of infection in the MenACWY control group. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped CIs for the relative risk. The arrows point to the immune marker values at 0.20 and 0.50 relative risk, that is 80% and 50% VE for illustrative purpose. The full range of VE estimates from 50 to 90% are shown in Table 2.
Fig. 2 Relative risk of primary symptomatic COVID-19 among vaccine recipients compared with MenACWY control arm participants as a function of immune markers measured at PB28. a, Anti-spike IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). b, Anti-RBD IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). c, Pseudovirus neutralization antibody titers at PB28 (47 cases, 828 noncases included in the analysis). d, Live-virus neutralization antibody titers at PB28 (36 cases, 412 noncases included in the analysis). Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared with that of the MenACWY control arm participants, derived by dividing the output curve from Fig. 1 by the overall risk of infection in the MenACWY control group. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped CIs for the relative risk. The arrows point to the immune marker values at 0.20 and 0.50 relative risk, that is 80% and 50% VE for illustrative purpose. The full range of VE estimates from 50 to 90% are shown in Table 2.CC BY · PubMed Central
Fig. 3 Relative risk of asymptomatic SARS-CoV-2 infection among vaccine recipients compared with the MenACWY control arm participants as a function of immune markers measured at PB28. a, Anti-spike IgG measured at PB28 (91 cases, 1,155 noncases included in the analysis). b, Anti-RBD IgG measured at PB28 (91 cases, 1,155 noncases included in the analysis). c, Pseudovirus neutralization antibody titers at PB28 (86 cases, 828 noncases included in the analysis). d, Live-virus neutralization antibody titers at PB28 (62 cases, 412 noncases included in the analysis). Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared with the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are bootstrapped 95% CIs.
Fig. 3 Relative risk of asymptomatic SARS-CoV-2 infection among vaccine recipients compared with the MenACWY control arm participants as a function of immune markers measured at PB28. a, Anti-spike IgG measured at PB28 (91 cases, 1,155 noncases included in the analysis). b, Anti-RBD IgG measured at PB28 (91 cases, 1,155 noncases included in the analysis). c, Pseudovirus neutralization antibody titers at PB28 (86 cases, 828 noncases included in the analysis). d, Live-virus neutralization antibody titers at PB28 (62 cases, 412 noncases included in the analysis). Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared with the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are bootstrapped 95% CIs.CC BY · PubMed Central
Fig. 4 VE against primary symptomatic COVID-19 as a function of immune markers measured at PB28. a, Anti-spike IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). b, Anti-RBD IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). c, Pseudovirus neutralization antibody titers at PB28 (47 cases, 828 noncases included in the analysis). d, Live-virus neutralization antibody titers at PB28 (36 cases, 412 noncases included in the analysis). Blue shaded areas represent the immune marker density distribution. Green lines show the VE, and green dotted lines are 95% bootstrapped confidence intervals for VE. VE is computed as 1 minus the relative risks shown in Fig. 2. These results are also shown in Table 2 at 10% increments on the y axis.
Fig. 4 VE against primary symptomatic COVID-19 as a function of immune markers measured at PB28. a, Anti-spike IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). b, Anti-RBD IgG measured at PB28 (52 cases, 1,155 noncases included in the analysis). c, Pseudovirus neutralization antibody titers at PB28 (47 cases, 828 noncases included in the analysis). d, Live-virus neutralization antibody titers at PB28 (36 cases, 412 noncases included in the analysis). Blue shaded areas represent the immune marker density distribution. Green lines show the VE, and green dotted lines are 95% bootstrapped confidence intervals for VE. VE is computed as 1 minus the relative risks shown in Fig. 2. These results are also shown in Table 2 at 10% increments on the y axis.CC BY · PubMed Central
Extended Data Fig. 1 Participant flow chart showing inclusion in correlates models. Eligible participants comprised the Correlates Population and those with samples processed comprised the Correlates Cohort.
Extended Data Fig. 1 Participant flow chart showing inclusion in correlates models. Eligible participants comprised the Correlates Population and those with samples processed comprised the Correlates Cohort.CC BY · PubMed Central
Extended Data Fig. 2 Immune markers measured at day 28 post-second dose, in primary symptomatic, asymptomatic, non-primary cases, NAAT positive cases and NAAT negative non-cases. a: N = 1155 NAAT negative, 52 primary, 91 asymptomatic and 20 non-primary, b: N = 163 NAAT positive participants’ anti-spike IgG measured at 28 days post boost; c: N = 1155 negative, 52 primary, 91 asymptomatic and 20 non-primary, d: N = 163 NAAT positive participants’ anti-RBD IgG measured at 28 days post boost; e: N = 828 NAAT negative, 47 primary, 86 asymptomatic and 16 non-primary, f: N = 149 NAAT positive participants’ pseudovirus neutralisation titre measured at 28 days post boost; g: N = 412 negative, 36 primary, 62 asymptomatic and 12 non-primary, h: N = 110 NAAT positive participants’ live neutralisation titre measured at 28 days post boost. a–h: minima: smallest value; maxima: largest value; centre: median value; bounds of box: 25% and 75% quartile value; upper/lower whisker extends from the hinge to the largest/smallest value no further than 1.5 * inter-quartile range from the hinge. IgG: Immunoglobulin G; RBD: receptor binding domain. Primary symptomatic cases: NAAT+ with at least one COVID symptom (cough, fever, shortness of breath, anosmia, aguesia). Asymptomatic cases: NAAT+ on weekly self-swab with no symptoms recorded. Non-primary cases: NAAT+ with only non-primary COVID symptoms (for example nausea, diarrhoea). P-value estimated by one-way ANOVA test comparing between primary, asymptomatic, non-primary cases and NAAT negative non-cases and by two sample t-test comparing between NAAT positive cases and NAAT negative non-cases (two-sided).
Extended Data Fig. 2 Immune markers measured at day 28 post-second dose, in primary symptomatic, asymptomatic, non-primary cases, NAAT positive cases and NAAT negative non-cases. a: N = 1155 NAAT negative, 52 primary, 91 asymptomatic and 20 non-primary, b: N = 163 NAAT positive participants’ anti-spike IgG measured at 28 days post boost; c: N = 1155 negative, 52 primary, 91 asymptomatic and 20 non-primary, d: N = 163 NAAT positive participants’ anti-RBD IgG measured at 28 days post boost; e: N = 828 NAAT negative, 47 primary, 86 asymptomatic and 16 non-primary, f: N = 149 NAAT positive participants’ pseudovirus neutralisation titre measured at 28 days post boost; g: N = 412 negative, 36 primary, 62 asymptomatic and 12 non-primary, h: N = 110 NAAT positive participants’ live neutralisation titre measured at 28 days post boost. a–h: minima: smallest value; maxima: largest value; centre: median value; bounds of box: 25% and 75% quartile value; upper/lower whisker extends from the hinge to the largest/smallest value no further than 1.5 * inter-quartile range from the hinge. IgG: Immunoglobulin G; RBD: receptor binding domain. Primary symptomatic cases: NAAT+ with at least one COVID symptom (cough, fever, shortness of breath, anosmia, aguesia). Asymptomatic cases: NAAT+ on weekly self-swab with no symptoms recorded. Non-primary cases: NAAT+ with only non-primary COVID symptoms (for example nausea, diarrhoea). P-value estimated by one-way ANOVA test comparing between primary, asymptomatic, non-primary cases and NAAT negative non-cases and by two sample t-test comparing between NAAT positive cases and NAAT negative non-cases (two-sided).CC BY · PubMed Central
Extended Data Fig. 3 Correlations between a, Anti-SARS-CoV-2 spike and RBD IgG. b, Anti-SARS-CoV-2 Spike IgG and pseudovirus neutralisation titre. c, Anti-SARS-CoV-2 Spike IgG and live virus neutralisation titre. d, pseudovirus neutralisation titres and live virus neutralisation titres. 95% confidence ellipses assuming a t-distribution are shown for each outcome (primary symptomatic cases, asymptomatic cases and negative controls). Pearson correlation coefficients shown as r values using all available data. Primary symptomatic cases: NAAT+ with at least one COVID symptom (cough, fever, shortness of breath, anosmia, aguesia). Asymptomatic cases: NAAT+ on weekly self-swab with no symptoms recorded.
Extended Data Fig. 3 Correlations between a, Anti-SARS-CoV-2 spike and RBD IgG. b, Anti-SARS-CoV-2 Spike IgG and pseudovirus neutralisation titre. c, Anti-SARS-CoV-2 Spike IgG and live virus neutralisation titre. d, pseudovirus neutralisation titres and live virus neutralisation titres. 95% confidence ellipses assuming a t-distribution are shown for each outcome (primary symptomatic cases, asymptomatic cases and negative controls). Pearson correlation coefficients shown as r values using all available data. Primary symptomatic cases: NAAT+ with at least one COVID symptom (cough, fever, shortness of breath, anosmia, aguesia). Asymptomatic cases: NAAT+ on weekly self-swab with no symptoms recorded.CC BY · PubMed Central
Extended Data Fig. 4 Predicted absolute risk of asymptomatic SARS-CoV-2 infection as a function of immune markers measured 28 days post second dose. Predicted absolute risk of asymptomatic infection as a function of: a: Anti-spike IgG measured at 28 days post boost (91 cases, 1155 non-cases included in the analysis). b: Anti-RBD IgG measured at 28 days post boost (91 cases, 1155 non-cases included in the analysis). c: Pseudovirus neutralisation antibody titres 28 days post boost (86 cases, 828 non-cases included in the analysis). d: Live-virus neutralisation antibody titres 28 days post boost (62 cases, 412 non-cases included in the analysis). Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line).
Extended Data Fig. 4 Predicted absolute risk of asymptomatic SARS-CoV-2 infection as a function of immune markers measured 28 days post second dose. Predicted absolute risk of asymptomatic infection as a function of: a: Anti-spike IgG measured at 28 days post boost (91 cases, 1155 non-cases included in the analysis). b: Anti-RBD IgG measured at 28 days post boost (91 cases, 1155 non-cases included in the analysis). c: Pseudovirus neutralisation antibody titres 28 days post boost (86 cases, 828 non-cases included in the analysis). d: Live-virus neutralisation antibody titres 28 days post boost (62 cases, 412 non-cases included in the analysis). Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line).CC BY · PubMed Central
Extended Data Fig. 5 Sensitivity analysis showing absolute and relative risk of asymptomatic SARS-CoV-2 infection as a function of immune markers measured at 28 days post second dose excluding cases with low viral load (Ct ≥ 30). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line). b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.
Extended Data Fig. 5 Sensitivity analysis showing absolute and relative risk of asymptomatic SARS-CoV-2 infection as a function of immune markers measured at 28 days post second dose excluding cases with low viral load (Ct ≥ 30). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line). b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.CC BY · PubMed Central
Extended Data Fig. 6 Sensitivity analysis showing absolute and relative risk of primary symptomatic SARS-CoV-2 infection in participants with symptoms of shortness of breath as a function of immune markers measured at day 28 post-second dose. Results are shown for: a, b: Anti-spike IgG measured at 28 days post boost (28 cases, 1155 non-cases included in the analysis). c, d: Anti-RBD IgG measured at 28 days post boost (28 cases, 1155 non-cases included in the analysis). e, f: Pseudovirus neutralisation antibody titres 28 days post boost (27 cases, 828 non-cases included in the analysis). g, h: Live virus neutralisation antibody titres 28 days post boost (22 cases, 412 non-cases included in the analysis). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line) b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.
Extended Data Fig. 6 Sensitivity analysis showing absolute and relative risk of primary symptomatic SARS-CoV-2 infection in participants with symptoms of shortness of breath as a function of immune markers measured at day 28 post-second dose. Results are shown for: a, b: Anti-spike IgG measured at 28 days post boost (28 cases, 1155 non-cases included in the analysis). c, d: Anti-RBD IgG measured at 28 days post boost (28 cases, 1155 non-cases included in the analysis). e, f: Pseudovirus neutralisation antibody titres 28 days post boost (27 cases, 828 non-cases included in the analysis). g, h: Live virus neutralisation antibody titres 28 days post boost (22 cases, 412 non-cases included in the analysis). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line) b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.CC BY · PubMed Central
Extended Data Fig. 7 Sensitivity analysis showing absolute and relative risk of primary symptomatic SARS-CoV-2 infection in participants with no symptoms of shortness of breath as a function of immune markers measured at day 28 post-second dose. Results are shown for: a, b: Anti-spike IgG measured at 28 days post boost (24 cases, 1155 non-cases included in the analysis). c, d: Anti-RBD IgG measured at 28 days post boost (24 cases, 1155 non-cases included in the analysis). e, f: Pseudovirus neutralisation antibody titres 28 days post boost (20 cases, 828 non-cases included in the analysis). g, h: Live virus neutralisation antibody titres 28 days post boost (14 cases, 412 non-cases included in the analysis). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line). b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.
Extended Data Fig. 7 Sensitivity analysis showing absolute and relative risk of primary symptomatic SARS-CoV-2 infection in participants with no symptoms of shortness of breath as a function of immune markers measured at day 28 post-second dose. Results are shown for: a, b: Anti-spike IgG measured at 28 days post boost (24 cases, 1155 non-cases included in the analysis). c, d: Anti-RBD IgG measured at 28 days post boost (24 cases, 1155 non-cases included in the analysis). e, f: Pseudovirus neutralisation antibody titres 28 days post boost (20 cases, 828 non-cases included in the analysis). g, h: Live virus neutralisation antibody titres 28 days post boost (14 cases, 412 non-cases included in the analysis). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line). b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.CC BY · PubMed Central
Extended Data Fig. 8 Sensitivity analysis showing absolute and relative risk primary symptomatic SARS-CoV-2 infection with 3 or more COVID-19 symptoms as a function of immune markers measured at day 28 post-second dose. Results are shown for: a, b: Anti-spike IgG measured at 28 days post boost (32 cases, 1155 non-cases included in the analysis). c, d: Anti-RBD IgG measured at 28 days post boost (32 cases, 1155 non-cases included in the analysis). e, f: Pseudovirus neutralisation antibody titres 28 days post boost (28 cases, 828 non-cases included in the analysis). g, h: Live virus neutralisation antibody titres 28 days post boost (21 cases, 412 non-cases included in the analysis). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line). b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.
Extended Data Fig. 8 Sensitivity analysis showing absolute and relative risk primary symptomatic SARS-CoV-2 infection with 3 or more COVID-19 symptoms as a function of immune markers measured at day 28 post-second dose. Results are shown for: a, b: Anti-spike IgG measured at 28 days post boost (32 cases, 1155 non-cases included in the analysis). c, d: Anti-RBD IgG measured at 28 days post boost (32 cases, 1155 non-cases included in the analysis). e, f: Pseudovirus neutralisation antibody titres 28 days post boost (28 cases, 828 non-cases included in the analysis). g, h: Live virus neutralisation antibody titres 28 days post boost (21 cases, 412 non-cases included in the analysis). a, c, e, g: Grey horizontal lines show the overall risk of primary symptomatic COVID-19 in the control group (MenACWY) and vaccine groups (ChAdOx1 nCoV-19). Blue dots show the absolute risk predicted from the model across the range of antibody values included in the analysis, adjusting for baseline exposure risk to SARS-CoV-2 infection. Green shaded areas show the confidence interval around the predicted mean probability (green line). b, d, f, h: Blue shaded areas represent the immune marker density distribution. Green lines show the relative risk of infection among vaccine recipients compared to the MenACWY control arm participants. The green lines are the median relative risk obtained from 10,000 bootstrap samples. Green shaded areas are 95% bootstrapped confidence intervals for the relative risk.CC BY · PubMed Central

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    “We assume the mechanism of missingness for samples that were not tested to be missing at random 39 .”
  • The paper relies on this without support.

    No study to date has defined a correlate of protection against SARS-CoV-2 infection or disease that can be used by regulators and vaccine developers.

    “Nevertheless, no study to date has defined a correlate of protection against SARS-CoV-2 infection or disease that can be used by regulators and vaccine developers.”
  • The paper relies on this without support.

    Baseline exposure risk predicted from the MenACWY control population is applicable to the ChAdOx1 nCoV-19 correlates cohort.

    “The linear predictor from the risk model developed using the MenACWY control population was used to predict the baseline risk of exposure in the ChAdOx1 nCoV-19 correlates cohort.”
  • The authors state this as an assumption.

    The confidence ellipses for correlations assume a t-distribution.

    “95% confidence ellipses assuming a t-distribution are shown for each outcome (primary symptomatic cases, asymptomatic cases and negative controls).”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Citations

Cites

Show all 41 references

Research works printed but not linked: 2

  1. Kemp, A. AZD1222 US Phase III trial met primary efficacy endpoint in preventing COVID-19 at interim analysis. https://www.astrazeneca.com/media-centre/press-releases/2021/astrazeneca-us-vaccine-trial-met-primary-endpoint.html (2021).
  2. Box, G. E. & Tiao, G. C. Bayesian Inference in Statistical Analysis (John Wiley & Sons, 2011).

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Metadata

Authors
Feng, S., Phillips, D. J., White, T., Sayal, H., Aley, P. K., Bibi, S., Dold, C., Fuskova, M., Gilbert, S. C., Hirsch, I., Humphries, H. E., Jepson, B., Kelly, E. J., Plested, E., Shoemaker, K., Thomas, K. M., Vekemans, J., Villafana, T. L., Lambe, T., Pollard, A. J., Voysey, M., the Oxford COVID Vaccine Trial Group, Adlou, S., Allen, L., Angus, B., Anslow, R., Asselin, M.-C., Baker, N., Baker, P., Barlow, T., Beveridge, A., Bewley, K. R., Brown, P., Brunt, E., Buttigieg, K. R., Camara, S., Charlton, S., Chiplin, E., Cicconi, P., Clutterbuck, E. A., Collins, A. M., Coombes, N. S., Clemens, S. A. C., Davison, M., Demissie, T., Dinesh, T., Douglas, A. D., Duncan, C. J. A., Emary, K. R. W., Ewer, K. J., Felle, S., Ferreira, D. M., Finn, A., Folegatti, P. M., Fothergill, R., Fraser, S., Garlant, H., Gatcombe, L., Godwin, K. J., Goodman, A. L., Green, C. A., Hallis, B., Hart, T. C., Heath, P. T., Hill, H., Hill, A. V. S., Jenkin, D., Kasanyinga, M., Kerridge, S., Knight, C., Leung, S., Libri, V., Lillie, P. J., Marinou, S., McGlashan, J., McGregor, A. C., McInroy, L., Minassian, A. M., Mujadidi, Y. F., Penn, E. J., Petropoulos, C. J., Pollock, K. M., Proud, P. C., Provstgaard-Morys, S., Rajapaska, D., Ramasamy, M. N., Sanders, K., Shaik, I., Singh, N., Smith, A., Snape, M. D., Song, R., Shrestha, S., Sutherland, R. K., Thomson, E. C., Turner, D. P. J., Webb-Bridges, A., Wrin, T., & Williams, C. J.
Affiliations
  • University of Oxford (GB)
  • AstraZeneca (United Kingdom) (GB)
  • Public Health England (GB)
  • AstraZeneca (United States) (US)
  • AstraZeneca (Sweden) (SE)
  • Liverpool School of Tropical Medicine (GB)
  • University of Siena (IT)
  • Newcastle upon Tyne Hospitals NHS Foundation Trust (GB)
  • University of Bristol (GB)
  • St Thomas' Hospital (GB)
  • University Hospitals Birmingham NHS Foundation Trust (GB)
  • St George's, University of London (GB)
  • University of Hull (GB)
  • London North West Healthcare NHS Trust (GB)
  • LabCorp (United States) (US)
  • NHS Lothian (GB)
  • Nottingham University Hospitals NHS Trust (GB)
  • Aneurin Bevan University Health Board (GB)
Corresponding author
Voysey, Merryn
Venue
Nature Medicine
Published
2021-09-29
Volume
27
Issue
11
Pages
2032-2040
ISSN
  • 1078-8956 (ISSN-L)
  • 1546-170X
OpenAlex
W3174017401
Cited by
1,163
References
41
Citations by year
2026: 36 · 2025: 94 · 2024: 155 · 2023: 255 · 2022: 515 · 2021: 106
FWCI
81.72
Type
journal article
Language
en
Open access
Locations
  • Nature Medicine (publishedVersion, cc-by)
  • medRxiv (acceptedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Repository@Nottingham (University of Nottingham) (publishedVersion, cc-by)
  • St George's Online Research Archive (St George's University of London) (acceptedVersion)
  • LSTM Online Archive (Liverpool School of Tropical Medicine) (acceptedVersion)
  • ePrints Soton (University of Southampton) (acceptedVersion)
  • Liverpool John Moores University (acceptedVersion)
  • LSHTM Research Online (London School of Hygiene and Tropical Medicine) (acceptedVersion)
  • UCL Discovery (University College London) (submittedVersion)
  • Repository@Nottingham (University of Nottingham) (submittedVersion, cc-by)
  • University of Birmingham Research Portal (University of Birmingham) (submittedVersion, other-oa)
  • Spiral (Imperial College London) (submittedVersion, cc-by)
Funders
DH | National Institute for Health Research (NA)
Topics
  • Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
  • Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
  • Life Sciences › Agricultural and Biological Sciences › Animal Science and Zoology › Animal Virus Infections Studies
Keywords
SARS-CoV-2, COVID-19 vaccines, vaccine efficacy, binding antibodies, neutralizing antibodies, anti-spike antibodies, anti-RBD antibodies, pseudovirus neutralization, symptomatic infection, asymptomatic infection, Alpha variant, vaccine correlates of protection, vaccine licensure
MeSH terms
COVID-19, SARS-CoV-2, COVID-19 Vaccines, Adolescent, Adult, Aged, Aged, 80 and over, Antibodies, Viral, Female, United Kingdom, Humans, Immunization, Secondary, Male, Middle Aged, Vaccination, Cohort Studies, Treatment Outcome, Infection Control, Young Adult, Immunity, Humoral, Antibodies, Neutralizing, Asymptomatic Infections, Patient Acuity

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

A language model drew the claims from the paper on 2026-10-06, under version 3 of the claim definition (model deepseek-v4.1-flash, prompt extract-v3).

A second model labelled each claim on 2026-10-06 (model jev-1.13-20260917, definition revision gold-guideline-v0.2).

Cited sources are checked with a language model’s help (gpt-6-sol).

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

What counts as a claim ›How we measure confidence ›How we check this ›

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