AstraZeneca vaccine doesn't protect against South African variant of COVID-19, shows trial
South Africa: Results from a phase 1b-2 clinical trial showed two-dose regimen of the AstraZeneca-Oxford University COVID-19 vaccine to be ineffective against mild-to-moderate COVID-19 due to the B.1.351 variant.The study, published in the New England Journal of Medicine, found that two-dose regimen of the ChAdOx1 nCoV-19 vaccine did not provide protection...
South Africa: Results from a phase 1b-2 clinical trial showed two-dose regimen of the AstraZeneca-Oxford University COVID-19 vaccine to be ineffective against mild-to-moderate COVID-19 due to the B.1.351 variant.
The study, published in the New England Journal of Medicine, found that two-dose regimen of the ChAdOx1 nCoV-19 vaccine did not provide protection against mild-to-moderate infections with the B1351 variant first identified in South Africa.
Safety and efficacy assessment of vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential in different population, so is investigation of the efficacy of the vaccines against emerging SARS-CoV-2 variants of concern, including the B.1.351 (501Y.V2).
Shabir A. Madhi and colleagues aimed 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.
For the purpose, the researchers conducted a multicenter, double-blind, randomized, controlled trial that included participants 18 to less than 65 years of age. They were assigned in a ratio of 1:1 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.
2026 HIV-negative adults were enrolled between June 24 and November 9, 2020; 1010 and 1011 participants received at least one dose of placebo or vaccine, respectively.
Key findings of the study include:
- 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%.
- Among the 42 participants with Covid-19, 39 cases (92.9%) were caused by the B.1.351 variant; vaccine efficacy against this variant, analyzed as a secondary end point, was 10.4%.
- The incidence of serious adverse events was balanced between the vaccine and placebo groups.
"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," wrote the authors.
The study titled, "Efficacy of the ChAdOx1 nCoV-19 Covid-19 Vaccine against the B.1.351 Variant," is published in the New England Journal of Medicine.
Medha, MSc. Biotechnology
Medha Baranwal joined Medical Dialogues as an Editor in 2018 for Speciality Medical Dialogues. She covers several medical specialties including Cardiac Sciences, Dentistry, Diabetes and Endo, Diagnostics, ENT, Gastroenterology, Neurosciences, and Radiology. She has completed her Bachelors in Biomedical Sciences from DU and then pursued Masters in Biotechnology from Amity University. She has a working experience of 5 years in the field of medical research writing, scientific writing, content writing, and content management. She can be contacted at email@example.com. Contact no. 011-43720751