CoChat
Sign Up
Cited by 4,616SARS-CoV-2 and COVID-19 ResearchCOVID-19 Clinical Research StudiesVaccine Coverage and Hesitancy

Safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) against SARS-CoV-2: an interim analysis of four randomised controlled trials in Brazil, South Africa, and the UK

Open access
Voysey, Merryn, Clemens, Sue Ann Costa, Madhi, Shabir A, Weckx, Lily Y, Folegatti, Pedro M, Aley, Parvinder K, Angus, Brian, Baillie, Vicky L +757 more·2021·The Lancet
DOI 10.1016/s0140-6736(20)32661-1PMC PMC7723445
Open this paper in CoChat — free accountOpen PDF

Abstract

Background A safe and efficacious vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), if deployed with high coverage, could contribute to the control of the COVID-19 pandemic. We evaluated the safety and efficacy of the ChAdOx1 nCoV-19 vaccine in a pooled interim analysis of four trials. Methods This analysis includes data from four ongoing blinded, randomised, controlled trials done across the UK, Brazil, and South Africa. Participants aged 18 years and older were randomly assigned (1:1) to ChAdOx1 nCoV-19 vaccine or control (meningococcal group A, C, W, and Y conjugate vaccine or saline). Participants in the ChAdOx1 nCoV-19 group received two doses containing 5 × 10 10 viral particles (standard dose; SD/SD cohort); a subset in the UK trial received a half dose as their first dose (low dose) and a standard dose as their second dose (LD/SD cohort). The primary efficacy analysis included symptomatic COVID-19 in seronegative participants with a nucleic acid amplification test-positive swab more than 14 days after a second dose of vaccine. Participants were analysed according to treatment received, with data cutoff on Nov 4, 2020. Vaccine efficacy was calculated as 1 - relative risk derived from a robust Poisson regression model adjusted for age. Studies are registered at ISRCTN89951424 and ClinicalTrials.gov, NCT04324606, NCT04400838, and NCT04444674. Findings Between April 23 and Nov 4, 2020, 23 848 participants were enrolled and 11 636 participants (7548 in the UK, 4088 in Brazil) were included in the interim primary efficacy analysis. In participants who received two standard doses, vaccine efficacy was 62·1% (95% CI 41·0–75·7; 27 [0·6%] of 4440 in the ChAdOx1 nCoV-19 group vs 71 [1·6%] of 4455 in the control group) and in participants who received a low dose followed by a standard dose, efficacy was 90·0% (67·4–97·0; three [0·2%] of 1367 vs 30 [2·2%] of 1374; p interaction =0·010). Overall vaccine efficacy across both groups was 70·4% (95·8% CI 54·8–80·6; 30 [0·5%] of 5807 vs 101 [1·7%] of 5829). From 21 days after the first dose, there were ten cases hospitalised for COVID-19, all in the control arm; two were classified as severe COVID-19, including one death. There were 74 341 person-months of safety follow-up (median 3·4 months, IQR 1·3–4·8): 175 severe adverse events occurred in 168 participants, 84 events in the ChAdOx1 nCoV-19 group and 91 in the control group. Three events were classified as possibly related to a vaccine: one in the ChAdOx1 nCoV-19 group, one in the control group, and one in a participant who remains masked to group allocation. Interpretation ChAdOx1 nCoV-19 has an acceptable safety profile and has been found to be efficacious against symptomatic COVID-19 in this interim analysis of ongoing clinical trials. Funding UK Research and Innovation, National Institutes for Health Research (NIHR), Coalition for Epidemic Preparedness Innovations, Bill & Melinda Gates Foundation, Lemann Foundation, Rede D'Or, Brava and Telles Foundation, NIHR Oxford Biomedical Research Centre, Thames Valley and South Midland's NIHR Clinical Research Network, and AstraZeneca.

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

Integrity signals

Registry

Crossref · 10.1016/s0140-6736(20)32661-1

Cites

10 of 10 references verified0 citation errors · 0 not checkable

Statistics

Claims the paper makes

The claims and statistics of this paper haven’t been checked yet.

Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.

A few free checks a day · papers already verified open instantly · results are public

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?

  • The interim phase 3 results of other COVID-19 vaccines have shown efficacies ranging from 62.1% to 95%.

    “The interim phase 3 results of other COVID-19 vaccines have shown efficacies ranging from 62·1% to 95%.24, 25, 26, 27, 28”

    From Efficacy and safety of an inactivated whole-virion SARS-CoV-2 vaccine (CoronaVac): interim results of a double-blind, randomised, placebo-controlled, phase 3 trial in Turkey (2021) · cites this paper as [27]

    Table 2 in the Results reports 62·1% efficacy for standard-dose ChAdOx1 recipients in this interim analysis. The Research in context passage reports 95% for Pfizer/BioNTech, but identifies that figure as coming from a primary analysis, not an interim analysis. Thus the range is supported, but the sentence's 'interim' qualifier does not fit both endpoints. (LLM, conf=0.86)

    Experimental — accuracy not yet measured

  • A single dose of adenovirus-vectored vaccines induces polyfunctional antibodies that neutralize virus and mediate other antibody-dependent effector functions, plus strong T cell responses.

    “After a single dose, the adenovirus vaccines elicit polyfunctional antibodies that are capable of mediating virus neutralization and of driving other antibody-dependent effector functions, as well as potent T cell responses.”

    From Immunological mechanisms of vaccine-induced protection against COVID-19 in humans (2021) · cites this paper as [87]

  • ChAdOx-1 nCoV-19 had about 70% efficacy against symptomatic COVID-19 after one or two doses.

    “There was ~70% efficacy for ChAdOx-1 nCoV-19 (after one or two doses)87,88 and Ad26.COV2.S (after one dose)89 (Table 1).”

    From Immunological mechanisms of vaccine-induced protection against COVID-19 in humans (2021) · cites this paper as [87]

  • Vaccines lacking pre-fusion stabilization, such as ChAdOx1 nCoV-19, have demonstrated efficacy.

    “However, vaccines without this stabilization (for example, ChAdOx1 nCoV-19) have proven efficacy and so the importance of this for COVID-19 vaccines is uncertain.”

    From Immunological mechanisms of vaccine-induced protection against COVID-19 in humans (2021) · cites this paper as [87]

  • A second dose provides additional benefit for Gam-COVID-Vac, with efficacy around 90%.

    “Additional benefit of a second dose is evident for Gam-COVID-Vac, when efficacy is ~90%87–90 (Table 1; see Supplementary Figure 1).”

    From Immunological mechanisms of vaccine-induced protection against COVID-19 in humans (2021) · cites this paper as [87]

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

The self-check needs the paper’s full text.

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. [11]Pfizer Pfizer and BioNTech announce vaccine candidate against COVID-19 achieved success in first interim analysis from phase 3 study https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-vaccine-candidate-against Nov 9, 2020
  2. [16]Bartsch SM O'Shea KJ Ferguson MC Vaccine efficacy needed for a COVID-19 coronavirus vaccine to prevent or stop an epidemic as the sole intervention Am J Prev Med 59 2020 493 503 32778354 PMC7361120

Cited by

Sorted by citations

Authors
Voysey, M., Clemens, S. A. C., Madhi, S. A., Weckx, L. Y., Folegatti, P. M., Aley, P. K., Angus, B., Baillie, V. L., Barnabas, S. L., Bhorat, Q. E., Bibi, S., Briner, C., Cicconi, P., Collins, A. M., Colin-Jones, R., Cutland, C. L., Darton, T. C., Dheda, K., Duncan, C. J. A., Emary, K. R. W., Ewer, K. J., Fairlie, L., Faust, S. N., Feng, S., Ferreira, D. M., Finn, A., Goodman, A. L., Green, C. M., Green, C. A., Heath, P. T., Hill, C., Hill, H., Hirsch, I., Hodgson, S. H. C., Izu, A., Jackson, S., Jenkin, D., Joe, C. C. D., Kerridge, S., Koen, A., Kwatra, G., Lazarus, R., Lawrie, A. M., Lelliott, A., Libri, V., Lillie, P. J., Mallory, R., Mendes, A. V. A., Milan, E. P., Minassian, A. M., McGregor, A., Morrison, H., Mujadidi, Y. F., Nana, A., O’Reilly, P. J., Padayachee, S. D., Pittella, A., Plested, E., Pollock, K. M., Ramasamy, M. N., Rhead, S., Schwarzbold, A. V., Singh, N., Smith, A., Song, R., Snape, M. D., Sprinz, E., Sutherland, R. K., Tarrant, R., Thomson, E. C., Török, M. E., Toshner, M., Turner, D. P. J., Vekemans, J., Villafana, T. L., Watson, M. E. E., Williams, C. J., Douglas, A. D., Hill, A. V. S., Lambe, T., Gilbert, S. C., Pollard, A. J., Aban, M., Abayomi, F., Abeyskera, K., Aboagye, J., Adam, M., Adams, K., Adamson, J., Adelaja, Y. A., Adewetan, G., Adlou, S., Ahmed, K., Akhalwaya, Y., Akhalwaya, S., Alcock, A., Ali, A., Allen, E. R., Allen, L., Almeida, T. C. D. S. C., Alves, M. P. S., Amorim, F., Andritsou, F., Anslow, R., Appleby, M., Arbe-Barnes, E. H., Ariaans, M. P., Arns, B., Arruda, L., Azi, P., Azi, L., Babbage, G., Bailey, C., Baker, K. F., Baker, M., Baker, N., Baker, P., Baldwin, L., Baleanu, I., Bandeira, D., Bara, A., Barbosa, M. A. S., Barker, D., Barlow, G. D., Barnes, E., Barr, A. S., Barrett, J. R., Barrett, J., Bates, L., Batten, A., Beadon, K., Beales, E., Beckley, R., Belij-Rammerstorfer, S., Bell, J., Bellamy, D., Bellei, N., Belton, S., Berg, A., Bermejo, L., Berrie, E., Berry, L., Berzenyi, D., Beveridge, A., Bewley, K. R., Bexhell, H., Bhikha, S., Bhorat, A. E., Bhorat, Z. E., Bijker, E., Birch, G., Birch, S., Bird, A., Bird, O., Bisnauthsing, K., Bittaye, M., Blackstone, K., Blackwell, L., Bletchly, H., Blundell, C. L., Blundell, S. R., Bodalia, P., Boettger, B. C., Bolam, E., Boland, E., Bormans, D., Borthwick, N., Bowring, F., Boyd, A., Bradley, P., Brenner, T., Brown, P., Brown, C., Brown-O'Sullivan, C., Bruce, S., Brunt, E., Buchan, R., Budd, W., Bulbulia, Y. A., Bull, M., Burbage, J., Burhan, H., Burn, A., Buttigieg, K. R., Byard, N., Cabera Puig, I., Calderon, G., Calvert, A., Camara, S., Cao, M., Cappuccini, F., Cardoso, J. R., Carr, M., Carroll, M. W., Carson-Stevens, A., Carvalho, Y. D. M., Carvalho, J. A. M., Casey, H. R., Cashen, P., Castro, T., Castro, L. C., Cathie, K., Cavey, A., Cerbino-Neto, J., Chadwick, J., Chapman, D., Charlton, S., Chelysheva, I., Chester, O., Chita, S., Cho, J.-S., Cifuentes, L., Clark, E., Clark, M., Clarke, A., Clutterbuck, E. A., Collins, S. L. K., Conlon, C. P., Connarty, S., Coombes, N., Cooper, C., Cooper, R., Cornelissen, L., Corrah, T., Cosgrove, C., Cox, T., Crocker, W. E. M., Crosbie, S., Cullen, L., Cullen, D., Cunha, D. R. M. F., Cunningham, C., Cuthbertson, F. C., Da Guarda, S. N. F., da Silva, L. P., Damratoski, B. E., Danos, Z., Dantas, M. T. D. C., Darroch, P., Datoo, M. S., Datta, C., Davids, M., Davies, S. L., Davies, H., Davis, E., Davis, J., Davis, J., De Nobrega, M. M. D., De Oliveira Kalid, L. M., Dearlove, D., Demissie, T., Desai, A., Di Marco, S., Di Maso, C., Dinelli, M. I. S., Dinesh, T., Docksey, C., Dold, C., Dong, T., Donnellan, F. R., Dos Santos, T., dos Santos, T. G., Dos Santos, E. P., Douglas, N., Downing, C., Drake, J., Drake-Brockman, R., Driver, K., Drury, R., Dunachie, S. J., Durham, B. S., Dutra, L., Easom, N. J. W., van Eck, S., Edwards, M., Edwards, N. J., El Muhanna, O. M., Elias, S. C., Elmore, M., English, M., Esmail, A., Essack, Y. M., Farmer, E., Farooq, M., Farrar, M., Farrugia, L., Faulkner, B., Fedosyuk, S., Felle, S., Feng, S., Ferreira Da Silva, C., Field, S., Fisher, R., Flaxman, A., Fletcher, J., Fofie, H., Fok, H., Ford, K. J., Fowler, J., Fraiman, P. H. A., Francis, E., Franco, M. M., Frater, J., Freire, M. S. M., Fry, S. H., Fudge, S., Furze, J., Fuskova, M., Galian-Rubio, P., Galiza, E., Garlant, H., Gavrila, M., Geddes, A., Gibbons, K. A., Gilbride, C., Gill, H., Glynn, S., Godwin, K., Gokani, K., Goldoni, U. C., Goncalves, M., Gonzalez, I. G. S., Goodwin, J., Goondiwala, A., Gordon-Quayle, K., Gorini, G., Grab, J., Gracie, L., Greenland, M., Greenwood, N., Greffrath, J., Groenewald, M. M., Grossi, L., Gupta, G., Hackett, M., Hallis, B., Hamaluba, M., Hamilton, E., Hamlyn, J., Hammersley, D., Hanrath, A. T., Hanumunthadu, B., Harris, S. A., Harris, C., Harris, T., Harrison, T. D., Harrison, D., Hart, T. C., Hartnell, B., Hassan, S., Haughney, J., Hawkins, S., Hay, J., Head, I., Henry, J., Hermosin Herrera, M., Hettle, D. B., Hill, J., Hodges, G., Horne, E., Hou, M. M., Houlihan, C., Howe, E., Howell, N., Humphreys, J., Humphries, H. E., Hurley, K., Huson, C., Hyder-Wright, A., Hyams, C., Ikram, S., Ishwarbhai, A., Ivan, M., Iveson, P., Iyer, V., Jackson, F., De Jager, J., Jaumdally, S., Jeffers, H., Jesudason, N., Jones, B., Jones, K., Jones, E., Jones, C., Jorge, M. R., Jose, A., Joshi, A., Júnior, E. A. M. S., Kadziola, J., Kailath, R., Kana, F., Karampatsas, K., Kasanyinga, M., Keen, J., Kelly, E. J., Kelly, D. M., Kelly, D., Kelly, S., Kerr, D., Kfouri, R. D. Á., Khan, L., Khozoee, B., Kidd, S., Killen, A., Kinch, J., Kinch, P., King, L. D. W., King, T. B., Kingham, L., Klenerman, P., Knapper, F., Knight, J. C., Knott, D., Koleva, S., Lang, M., Lang, G., Larkworthy, C. W., Larwood, J. P. J., Law, R., Lazarus, E. M., Leach, A., Lees, E. A., Lemm, N.-M., Lessa, A., Leung, S., Li, Y., Lias, A. M., Liatsikos, K., Linder, A., Lipworth, S., Liu, S., Liu, X., Lloyd, A., Lloyd, S., Loew, L., Lopez Ramon, R., Lora, L., Lowthorpe, V., Luz, K., MacDonald, J. C., MacGregor, G., Madhavan, M., Mainwaring, D. O., Makambwa, E., Makinson, R., Malahleha, M., Malamatsho, R., Mallett, G., Mansatta, K., Maoko, T., Mapetla, K., Marchevsky, N. G., Marinou, S., Marlow, E., Marques, G. N., Marriott, P., Marshall, R. P., Marshall, J. L., Martins, F. J., Masenya, M., Masilela, M., Masters, S. K., Mathew, M., Matlebjane, H., Matshidiso, K., Mazur, O., Mazzella, A., McCaughan, H., McEwan, J., McGlashan, J., McInroy, L., McIntyre, Z., McLenaghan, D., McRobert, N., McSwiggan, S., Megson, C., Mehdipour, S., Meijs, W., Mendonça, R. N. Á., Mentzer, A. J., Mirtorabi, N., Mitton, C., Mnyakeni, S., Moghaddas, F., Molapo, K., Moloi, M., Moore, M., Moraes-Pinto, M. I., Moran, M., Morey, E., Morgans, R., Morris, S., Morris, S., Morris, H. C., Morselli, F., Morshead, G., Morter, R., Mottal, L., Moultrie, A., Moya, N., Mpelembue, M., Msomi, S., Mugodi, Y., Mukhopadhyay, E., Muller, J., Munro, A., Munro, C., Murphy, S., Mweu, P., Myasaki, C. H., Naik, G., Naker, K., Nastouli, E., Nazir, A., Ndlovu, B., Neffa, F., Njenga, C., Noal, H., Noé, A., Novaes, G., Nugent, F. L., Nunes, G., O'Brien, K., O'Connor, D., Odam, M., Oelofse, S., Oguti, B., Olchawski, V., Oldfield, N. J., Oliveira, M. G., Oliveira, C., Oosthuizen, A., O'Reilly, P., Osborne, P., Owen, D. R. J., Owen, L., Owens, D., Owino, N., Pacurar, M., Paiva, B. V. B., Palhares, E. M. F., Palmer, S., Parkinson, S., Parracho, H. M. R. T., Parsons, K., Patel, D., Patel, B., Patel, F., Patel, K., Patrick-Smith, M., Payne, R. O., Peng, Y., Penn, E. J., Pennington, A., Peralta Alvarez, M. P., Perring, J., Perry, N., Perumal, R., Petkar, S., Philip, T., Phillips, D. J., Phillips, J., Phohu, M. K., Pickup, L., Pieterse, S., Piper, J., Pipini, D., Plank, M., Du Plessis, J., Pollard, S., Pooley, J., Pooran, A., Poulton, I., Powers, C., Presa, F. B., Price, D. A., Price, V., Primeira, M., Proud, P. C., Provstgaard-Morys, S., Pueschel, S., Pulido, D., Quaid, S., Rabara, R., Radford, A., Radia, K., Rajapaska, D., Rajeswaran, T., Ramos, A. S. F., Ramos Lopez, F., Rampling, T., Rand, J., Ratcliffe, H., Rawlinson, T., Rea, D., Rees, B., Reiné, J., Resuello-Dauti, M., Reyes Pabon, E., Ribiero, C. M., Ricamara, M., Richter, A., Ritchie, N., Ritchie, A. J., Robbins, A. J., Roberts, H., Robinson, R. E., Robinson, H., Rocchetti, T. T., Rocha, B. P., Roche, S., Rollier, C., Rose, L., Ross Russell, A. L., Rossouw, L., Royal, S., Rudiansyah, I., Ruiz, S., Saich, S., Sala, C., Sale, J., Salman, A. M., Salvador, N., Salvador, S., Sampaio, M., Samson, A. D., Sanchez-Gonzalez, A., Sanders, H., Sanders, K., Santos, E., Santos Guerra, M. F. S., Satti, I., Saunders, J. E., Saunders, C., Sayed, A., Schim van der Loeff, I., Schmid, A. B., Schofield, E., Screaton, G., Seddiqi, S., Segireddy, R. R., Senger, R., Serrano, S., Shah, R., Shaik, I., Sharpe, H. E., Sharrocks, K., Shaw, R., Shea, A., Shepherd, A., Shepherd, J. G., Shiham, F., Sidhom, E., Silk, S. E., da Silva Moraes, A. C., Silva-Junior, G., Silva-Reyes, L., Silveira, A. D., Silveira, M. B. V., Sinha, J., Skelly, D. T., Smith, D. C., Smith, N., Smith, H. E., Smith, D. J., Smith, C. C., Soares, A., Soares, T., Solórzano, C., Sorio, G. L., Sorley, K., Sosa-Rodriguez, T., Souza, C. M. C. D. L., Souza, B. S. D. F., Souza, A. R., Spencer, A. J., Spina, F., Spoors, L., Stafford, L., Stamford, I., Starinskij, I., Stein, R., Steven, J., Stockdale, L., Stockwell, L. V., Strickland, L. H., Stuart, A. C., Sturdy, A., Sutton, N., Szigeti, A., Tahiri-Alaoui, A., Tanner, R., Taoushanis, C., Tarr, A. W., Taylor, K., Taylor, U., Taylor, I. J., Taylor, J., te Water Naude, R., Themistocleous, Y., Themistocleous, A., Thomas, M., Thomas, K., Thomas, T. M., Thombrayil, A., Thompson, F., Thompson, A., Thompson, K., Thompson, A., Thomson, J., Thornton-Jones, V., Tighe, P. J., Tinoco, L. A., Tiongson, G., Tladinyane, B., Tomasicchio, M., Tomic, A., Tonks, S., Towner, J., Tran, N., Tree, J., Trillana, G., Trinham, C., Trivett, R., Truby, A., Tsheko, B. L., Turabi, A., Turner, R., Turner, C., Ulaszewska, M., Underwood, B. R., Varughese, R., Verbart, D., Verheul, M., Vichos, I., Vieira, T., Waddington, C. S., Walker, L., Wallis, E., Wand, M., Warbick, D., Wardell, T., Warimwe, G., Warren, S. C., Watkins, B., Watson, E., Webb, S., Webb-Bridges, A., Webster, A., Welch, J., Wells, J., West, A., White, C., White, R., Williams, P., Williams, R. L., Winslow, R., Woodyer, M., Worth, A. T., Wright, D., Wroblewska, M., Yao, A., Zimmer, R., Zizi, D., & Zuidewind, P.
Affiliations
  • University of Oxford (GB)
  • University of Siena (IT)
  • Universidade Federal de São Paulo (BR)
  • University of the Witwatersrand (ZA)
  • Stellenbosch University (ZA)
  • Soweto CTC (ZA)
  • Liverpool School of Tropical Medicine (GB)
  • Sheffield Teaching Hospitals NHS Foundation Trust (GB)
  • University of Cape Town (ZA)
  • Newcastle upon Tyne Hospitals NHS Foundation Trust (GB)
  • University Hospital Southampton 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)
  • AstraZeneca (United Kingdom) (GB)
  • North Bristol NHS Trust (GB)
  • UCL Biomedical Research Centre (GB)
  • University of Hull (GB)
  • Escola Bahiana de Medicina e Saúde Pública (BR)
  • Universidade Federal do Rio Grande do Norte (BR)
  • London North West Healthcare NHS Trust (GB)
  • Setshaba Research Centre (ZA)
  • Universidade Unigranrio (BR)
  • NIHR Imperial Biomedical Research Centre (GB)
  • Universidade Federal de Santa Maria (BR)
  • Boston Children's Hospital (US)
  • Universidade Federal do Rio Grande do Sul (BR)
  • Western General Hospital (GB)
  • MRC University of Glasgow Centre for Virus Research (GB)
  • University of Cambridge (GB)
  • Nottingham University Hospitals NHS Trust (GB)
  • Aneurin Bevan University Health Board (GB)
  • University of London (GB)
  • University College London Hospitals NHS Foundation Trust (GB)
Corresponding author
Pollard, Andrew J
ORCID
Venue
The Lancet
Publisher
Elsevier BV
Published
2021-01
Volume
397
Issue
10269
Pages
99-111
ISSN
  • 0099-5355 (ISSN-L)
  • 0140-6736
DOI
10.1016/s0140-6736(20)32661-1
PMC
PMC7723445
OpenAlex
W3111590711
Cited by
4,616
References
10
Citations by year
2026: 87 · 2025: 206 · 2024: 346 · 2023: 658 · 2022: 1388 · 2021: 1889 · 2020: 38 · 2019: 1
FWCI
130.43
Type
journal article
Language
en
Update notices
erratum (2021-01-09)
Open access
Licence
Locations
  • The Lancet (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Edinburgh Napier Research Repository (Edinburgh Napier University) (publishedVersion, other-oa)
  • LSTM Online Archive (Liverpool School of Tropical Medicine) (acceptedVersion)
  • ENLIGHTEN (Jurnal Bimbingan dan Konseling Islam) (acceptedVersion, cc-by-sa)
  • White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
  • ORCA Online Research @Cardiff (Cardiff University) (acceptedVersion)
  • St George's Online Research Archive (St George's University of London) (acceptedVersion)
  • Bristol Research (University of Bristol) (submittedVersion, cc-by)
  • LA Referencia (Red Federada de Repositorios Institucionales de Publicaciones Científicas) (submittedVersion, cc-by-nc-sa)
  • Arca - Repositório Institucional da Fiocruz (submittedVersion, other-oa)
  • ePrints Soton (University of Southampton) (submittedVersion, cc-by)
  • UCL Discovery (University College London) (submittedVersion)
  • University of Birmingham Research Portal (University of Birmingham) (submittedVersion, cc-by)
  • Edinburgh Research Explorer (University of Edinburgh) (submittedVersion, cc-by)
  • Edinburgh Napier Research Repository (Edinburgh Napier University) (submittedVersion, cc-by)
  • Spiral (Imperial College London) (submittedVersion, cc-by)
  • LA Referencia (Red Federada de Repositorios Institucionales de Publicaciones Científicas) (submittedVersion, other-oa)
  • Apollo (University of Cambridge) (submittedVersion, cc-by-nc-nd)
  • Apollo
Funders
  • Bill and Melinda Gates Foundation
  • AstraZeneca
  • Wellcome Trust (211153/Z/18/Z, 095541/A/11/Z, 109965/Z/15/Z)
  • Nottingham University Hospitals NHS Trust
  • UK Research and Innovation
  • Public Health Wales
  • Coalition for Epidemic Preparedness Innovations
  • Instituto D'Or de Pesquisa e Ensino
  • National Institute for Health and Care Research (ACF-2018-09-008, NF-SI-0617-10036, NIHR201409, CL-2018-13-007, CL‐2017‐01‐004, CL-2016-13-008, ACF-2018-01-004, NIHR202437, CL-2017-14-503, ACF-2018-01-001, ACF-2018-13-005, NIHR300791, CL-2016-04-502, CL-2013-01-003, NF-SI-0515-10005, COV19OxfordVaccine01, NF-SI-0617-10139)
  • Department of Health and Social Care
  • Academy of Medical Sciences (AMS-CSF4-Torok, AMS-SGCL11-Duncan, SGL023\1089)
  • University of Cambridge
  • University of Oxford
  • University of Nottingham
  • University of Glasgow
  • South African Medical Research Council
  • Cambridge University Hospitals (146281)
  • Universidade Federal do Rio Grande do Sul
  • Universidade Federal de Santa Maria
  • Fundação Lemann
  • Medical Research Council (MC_UU_00004/04, MC_UU_12023/22, MR/N008219/1, MC_PC_19026, MC_UU_12014/8, MR/L006588/1, MR/T001151/1, MR/T031891/1, MC_UU_00008/11, MR/L018942/1, MC_PC_18058)
  • Engineering and Physical Sciences Research Council (EP/R013756/1)
  • NIHR Imperial Biomedical Research Centre
  • NIHR Oxford Biomedical Research Centre
Topics
  • Health Sciences › Medicine › Infectious Diseases › SARS-CoV-2 and COVID-19 Research
  • Health Sciences › Medicine › Infectious Diseases › COVID-19 Clinical Research Studies
  • Social Sciences › Health › Vaccine Coverage and Hesitancy
Keywords
ChAdOx1 nCoV-19 vaccine, AZD1222, SARS-CoV-2, COVID-19 vaccines, vaccine efficacy, vaccine safety, viral vector vaccines, Brazil, South Africa
MeSH terms
COVID-19, COVID-19 Vaccines, ChAdOx1 nCoV-19, Adolescent, Adult, Aged, Brazil, Double-Blind Method, Female, United Kingdom, Humans, Male, Middle Aged, South Africa, Single-Blind Method, Treatment Outcome, Young Adult

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.

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 ›

Are you an author, or do you see a problem with this page? Request a review