Reactogenicity and immunogenicity after a late second dose or a third dose of ChAdOx1 nCoV-19 in the UK: a substudy of two randomised controlled trials (COV001 and COV002)

Flaxman, A. et al. (2021) Reactogenicity and immunogenicity after a late second dose or a third dose of ChAdOx1 nCoV-19 in the UK: a substudy of two randomised controlled trials (COV001 and COV002). Lancet, 398(10304), pp. 981-990. (doi: 10.1016/S0140-6736(21)01699-8) (PMID:34480858) (PMCID:PMC8409975)

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Background: COVID-19 vaccine supply shortages are causing concerns about compromised immunity in some countries as the interval between the first and second dose becomes longer. Conversely, countries with no supply constraints are considering administering a third dose. We assessed the persistence of immunogenicity after a single dose of ChAdOx1 nCoV-19 (AZD1222), immunity after an extended interval (44–45 weeks) between the first and second dose, and response to a third dose as a booster given 28–38 weeks after the second dose. Methods: In this substudy, volunteers aged 18–55 years who were enrolled in the phase 1/2 (COV001) controlled trial in the UK and had received either a single dose or two doses of 5 × 1010 viral particles were invited back for vaccination. Here we report the reactogenicity and immunogenicity of a delayed second dose (44–45 weeks after first dose) or a third dose of the vaccine (28–38 weeks after second dose). Data from volunteers aged 18–55 years who were enrolled in either the phase 1/2 (COV001) or phase 2/3 (COV002), single-blinded, randomised controlled trials of ChAdOx1 nCoV-19 and who had previously received a single dose or two doses of 5 × 1010 viral particles are used for comparison purposes. COV001 is registered with, NCT04324606, and ISRCTN, 15281137, and COV002 is registered with, NCT04400838, and ISRCTN, 15281137, and both are continuing but not recruiting. Findings: Between March 11 and 21, 2021, 90 participants were enrolled in the third-dose boost substudy, of whom 80 (89%) were assessable for reactogenicity, 75 (83%) were assessable for evaluation of antibodies, and 15 (17%) were assessable for T-cells responses. The two-dose cohort comprised 321 participants who had reactogenicity data (with prime-boost interval of 8–12 weeks: 267 [83%] of 321; 15–25 weeks: 24 [7%]; or 44–45 weeks: 30 [9%]) and 261 who had immunogenicity data (interval of 8–12 weeks: 115 [44%] of 261; 15–25 weeks: 116 [44%]; and 44–45 weeks: 30 [11%]). 480 participants from the single-dose cohort were assessable for immunogenicity up to 44–45 weeks after vaccination. Antibody titres after a single dose measured approximately 320 days after vaccination remained higher than the titres measured at baseline (geometric mean titre of 66·00 ELISA units [EUs; 95% CI 47·83–91·08] vs 1·75 EUs [1·60–1·93]). 32 participants received a late second dose of vaccine 44–45 weeks after the first dose, of whom 30 were included in immunogenicity and reactogenicity analyses. Antibody titres were higher 28 days after vaccination in those with a longer interval between first and second dose than for those with a short interval (median total IgG titre: 923 EUs [IQR 525–1764] with an 8–12 week interval; 1860 EUs [917–4934] with a 15–25 week interval; and 3738 EUs [1824–6625] with a 44–45 week interval). Among participants who received a third dose of vaccine, antibody titres (measured in 73 [81%] participants for whom samples were available) were significantly higher 28 days after a third dose (median total IgG titre: 3746 EUs [IQR 2047–6420]) than 28 days after a second dose (median 1792 EUs [IQR 899–4634]; Wilcoxon signed rank test p=0·0043). T-cell responses were also boosted after a third dose (median response increased from 200 spot forming units [SFUs] per million peripheral blood mononuclear cells [PBMCs; IQR 127–389] immediately before the third dose to 399 SFUs per milion PBMCs [314–662] by day 28 after the third dose; Wilcoxon signed rank test p=0·012). Reactogenicity after a late second dose or a third dose was lower than reactogenicity after a first dose. Interpretation: An extended interval before the second dose of ChAdOx1 nCoV-19 leads to increased antibody titres. A third dose of ChAdOx1 nCoV-19 induces antibodies to a level that correlates with high efficacy after second dose and boosts T-cell responses. Funding: UK Research and Innovation, Engineering and Physical Sciences Research Council, National Institute for Health Research, Coalition for Epidemic Preparedness Innovations, National Institute for Health Research Oxford Biomedical Research Centre, Chinese Academy of Medical Sciences Innovation Fund for Medical Science, Thames Valley and South Midlands NIHR Clinical Research Network, AstraZeneca, and Wellcome.

Item Type:Articles
Additional Information:Oxford University has entered into a partnership with AstraZeneca for further development of ChAdOx1 nCoV-19. We acknowledge funding for this study from the UK Research and Innovation (MC_PC_19055); Engineering and Physical Sciences Research Council (EP/R013756/1); National Institute for Health Research (COV19 OxfordVacc-01); Coalition for Epidemic Preparedness Innovations (Outbreak Response To Novel Coronavirus [COVID-19]); NIHR Oxford Biomedical Research Centre (BRC4 Vaccines Theme); The Chinese Academy of Medical Sciences (CAMS) Innovation Fund for Medical Science (CIFMS), China (2018-I2M-2-002; to AF and TL); Thames Valley and South Midlands NIHR Clinical Research Network; AstraZeneca; and the Wellcome Trust (220991/Z/20/Z).
Glasgow Author(s) Enlighten ID:Smith, Professor Andrew
Authors: Flaxman, A., Marchevsky, N. G., Jenkin, D., Aboagye, J., Aley, P. K., Angus, B., Belij-Rammerstorfer, S., Bibi, S., Bittaye, M., Cappuccini, F., Cicconi, P., Clutterbuck, E. A., Davies, S., Dejnirattisai, W., Dold, C., Ewer, K. J., Folegatti, P. M., Fowler, J., Hill, A. V. S., Kerridge, S., Minassian, A. M., Mongkolsapaya, J., Mujadidi, Y. F., Plested, E., Ramasamy, M. N., Robinson, H., Sanders, H., Sheehan, E., Smith, H., Snape, M. D., Song, R., Woods, D., Screaton, G., Gilbert, S. C., Voysey, M., Pollard, A. J., Lambe, T., Adlou, S., Aley, R., Ali, A., Anslow, R., Baker, M., Baker, P., Barrett, J. R., Bates, L., Beadon, K., Beckley, R., Bell, J., Bellamy, D., Beveridge, A., Bissett, C., Blackwell, L., Bletchly, H., Boyd, A., Bridges-Webb, A., Brown, C., Byard, N., Camara, S., Cifuentes Gutierrez, L., Collins, A. M., Cooper, R., Crocker, W. E.M., Darton, T. C., Davies, H., Davies, J., Demissie, T., Di Maso, C., Dinesh, T., Donnellan, F. R., Douglas, A. D., Drake-Brockman, R., Duncan, C. J.A., Elias, S. C., Emary, K. R.W., Ghulam Farooq, M., Faust, S. N., Felle, S., Ferreira, D., Ferreira Da Silva, C., Finn, A., Ford, K. J., Francis, E., Furze, J., Fuskova, M., Galiza, E., Gibertoni Cruz, A., Godfrey, L., Goodman, A. L., Green, C., Green, C. A., Greenwood, N., Harrison, D., Hart, T. C., Hawkins, S., Heath, P. T., Hill, H., Hillson, K., Horsington, B., Hou, M. M., Howe, E., Howell, N., Joe, C., Jones, E., Kasanyinga, M., Keen, J., Kelly, S., Kerr, D., Khan, L., Khozoee, B., Kinch, J., Kinch, P., Koleva, S., Kwok, J., Larkworthy, C. W., Lawrie, A. M., Lazarus, R., Lees, E. A., Li, G., Libri, V., Lillie, P. J., Linder, A., Long, F., Lopez Ramon, R., Mabbett, R., Makinson, R., Marinou, S., Marlow, E., Marshall, J. L., Mazur, O., McEwan, J., McGregor, A. C., Mokaya, J., Morey, E., Morshead, G., Morter, R., Muller, J., Mweu, P., Noristani, R., Owino, N., Polo Peralta Alvarez, M., Platt, A., Pollock, K. M., Poulton, I., Provstgaard-Morys, S., Pulido-Gomez, D., Rajan, M., Ramos Lopez, F., Ritchie, A., Roberts, H., Rollier, C., Rudiansyah, I., Sanders, K., Saunders, J. E., Seddiqi, S., Sharpe, H. R., Shaw, R., Silva-Reyes, L., Singh, N., Smith, D. J., Smith, C. C., Smith, A., Spencer, A. J., Stuart, A. S.V., Sutherland, R., Szigeti, A., Tang, K., Thomas, M., Thomas, T. M., Thompson, A., Thomson, E. C., Török, E. M., Toshner, M., Tran, N., Trivett, R., Turnbull, I., Turner, C., Turner, D. P.J., Ulaszewska, M., Vichos, I., Walker, L., Watson, M. E., Whelan, C., White, R., Williams, S. J., Williams, C. J.A., Wright, D., and Yao, A.
College/School:College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing > Dental School
Journal Name:Lancet
Publisher:The Lancet Publishing Group
ISSN (Online):1474-547X
Published Online:01 September 2021
Copyright Holders:Copyright © 2021 The Author(s).
First Published:First published in Lancet 398(10304):981-990
Publisher Policy:Reproduced under a Creative Commons Licence

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