Efficacy of primary series AZD1222 (ChAdOx1 nCoV-19) vaccination against SARS-CoV-2 variants of concern: Final analysis of a randomized, placebo-controlled, phase 1b/2 study in South African adults (COV005)

Vaccine. 2023 May 26;41(23):3486-3492. doi: 10.1016/j.vaccine.2023.04.058. Epub 2023 Apr 27.

Abstract

COVID-19 vaccine efficacy (VE) has been observed to vary against antigenically distinct SARS-CoV-2 variants of concern (VoC). Here we report the final analysis of VE and safety from COV005: a phase 1b/2, multicenter, double-blind, randomized, placebo-controlled study of primary series AZD1222 (ChAdOx1 nCoV-19) vaccination in South African adults aged 18-65 years. South Africa's first, second, and third waves of SARS-CoV-2 infections were respectively driven by the ancestral SARS-CoV-2 virus (wild type, WT), and SARS-CoV-2 Beta and Delta VoCs. VE against asymptomatic and symptomatic infection was 90.6% for WT, 6.7% for Beta and 77.1% for Delta. No cases of severe COVID-19 were documented ahead of unblinding. Safety was consistent with the interim analysis, with no new safety concerns identified. Notably, South Africa's Delta wave occurred ≥ 9 months after primary series vaccination, suggesting that primary series AZD1222 vaccination offers a good durability of protection, potentially due to an anamnestic response. Clinical trial identifier: CT.gov NCT04444674.

Keywords: AZD1222; COVID-19; ChAdOx1 nCov-19; SARS-CoV-2 variant; Vaccine efficacy.

Publication types

  • Randomized Controlled Trial
  • Multicenter Study
  • Clinical Trial, Phase II
  • Clinical Trial, Phase I
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • COVID-19 Vaccines / adverse effects
  • COVID-19* / prevention & control
  • ChAdOx1 nCoV-19*
  • Humans
  • SARS-CoV-2 / genetics
  • South Africa
  • Vaccination

Substances

  • ChAdOx1 nCoV-19
  • COVID-19 Vaccines

Supplementary concepts

  • SARS-CoV-2 variants

Associated data

  • ClinicalTrials.gov/NCT04444674