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

Authors :
Madhi SA
Baillie V
Cutland CL
Voysey M
Koen AL
Fairlie L
Padayachee SD
Dheda K
Barnabas SL
Bhorat QE
Briner C
Kwatra G
Ahmed K
Aley P
Bhikha S
Bhiman JN
Bhorat AE
du Plessis J
Esmail A
Groenewald M
Horne E
Hwa SH
Jose A
Lambe T
Laubscher M
Malahleha M
Masenya M
Masilela M
McKenzie S
Molapo K
Moultrie A
Oelofse S
Patel F
Pillay S
Rhead S
Rodel H
Rossouw L
Taoushanis C
Tegally H
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
Source :
The New England journal of medicine [N Engl J Med] 2021 May 20; Vol. 384 (20), pp. 1885-1898. Date of Electronic Publication: 2021 Mar 16.
Publication Year :
2021

Abstract

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.<br />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 5×10 <superscript>10</superscript> 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.<br />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.<br />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).<br /> (Copyright © 2021 Massachusetts Medical Society.)

Details

Language :
English
ISSN :
1533-4406
Volume :
384
Issue :
20
Database :
MEDLINE
Journal :
The New England journal of medicine
Publication Type :
Academic Journal
Accession number :
33725432
Full Text :
https://doi.org/10.1056/NEJMoa2102214