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).
Koen AL., Izu A., Baillie V., Kwatra G., Cutland CL., Fairlie L., Padayachee SD., Dheda K., Barnabas SL., Bhorat QE., Briner C., Ahmed K., Bhikha S., Bhiman JN., du Plessis J., Esmail A., Horne E., Hwa S-H., Oommen-Jose A., Lambe T., Laubscher M., Malahleha M., Benade G., McKenzie S., Oelofse S., Patel F., Pillay S., Rhead S., Rodel H., Taoushanis C., Tegally H., Thombrayil A., Villafana TL., Gilbert S., Pollard AJ., Madhi SA.
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.