Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant.

Madhi, SA; Baillie, V; Cutland, CL; Voysey, M; Koen, AL; Fairlie, L; Padayachee, SD; Dheda, KORCID logo; Barnabas, SL; Bhorat, QE; +43 more...Briner, C; Kwatra, G; Ahmed, K; Aley, P; Bhikha, S; Bhiman, JN; Bhorat, AE; du Plessis, J; Esmail, A; Groenewald, M; Horne, E; Hwa, S; Jose, A; Lambe, T; Laubscher, M; Malahleha, M; Masenya, M; Masilela, M; McKenzie, S; Molapo, K; Moultrie, AORCID logo; Oelofse, S; Patel, F; Pillay, S; Rhead, S; Rodel, H; Rossouw, L; Taoushanis, C; Tegally, HORCID logo; Thombrayil, A; van Eck, S; Wibmer, CK; Durham, NM; Kelly, EJ; Villafana, TL; Gilbert, S; Pollard, AJ; de Oliveira, T; Moore, PL; Sigal, A; Izu, A; NGS-SA Group; Wits-VIDA COVID Group and (2021) Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant. The New England journal of medicine, 384 (20). pp. 1885-1898. ISSN 0028-4793 DOI: 10.1056/NEJMoa2102214
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BACKGROUND: Assessment of the safety and efficacy of vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in different populations is essential, as is investigation of the efficacy of the vaccines against emerging SARS-CoV-2 variants of concern, including the B.1.351 (501Y.V2) variant first identified in South Africa. METHODS: We conducted a multicenter, double-blind, randomized, controlled trial to assess the safety and efficacy of the ChAdOx1 nCoV-19 vaccine (AZD1222) in people not infected with the human immunodeficiency virus (HIV) in South Africa. Participants 18 to less than 65 years of age were assigned in a 1:1 ratio to receive two doses of vaccine containing 5×1010 viral particles or placebo (0.9% sodium chloride solution) 21 to 35 days apart. Serum samples obtained from 25 participants after the second dose were tested by pseudovirus and live-virus neutralization assays against the original D614G virus and the B.1.351 variant. The primary end points were safety and efficacy of the vaccine against laboratory-confirmed symptomatic coronavirus 2019 illness (Covid-19) more than 14 days after the second dose. RESULTS: Between June 24 and November 9, 2020, we enrolled 2026 HIV-negative adults (median age, 30 years); 1010 and 1011 participants received at least one dose of placebo or vaccine, respectively. Both the pseudovirus and the live-virus neutralization assays showed greater resistance to the B.1.351 variant in serum samples obtained from vaccine recipients than in samples from placebo recipients. In the primary end-point analysis, mild-to-moderate Covid-19 developed in 23 of 717 placebo recipients (3.2%) and in 19 of 750 vaccine recipients (2.5%), for an efficacy of 21.9% (95% confidence interval [CI], -49.9 to 59.8). Among the 42 participants with Covid-19, 39 cases (95.1% of 41 with sequencing data) were caused by the B.1.351 variant; vaccine efficacy against this variant, analyzed as a secondary end point, was 10.4% (95% CI, -76.8 to 54.8). The incidence of serious adverse events was balanced between the vaccine and placebo groups. CONCLUSIONS: A two-dose regimen of the ChAdOx1 nCoV-19 vaccine did not show protection against mild-to-moderate Covid-19 due to the B.1.351 variant. (Funded by the Bill and Melinda Gates Foundation and others; ClinicalTrials.gov number, NCT04444674; Pan African Clinical Trials Registry number, PACTR202006922165132).


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