Efficacy of ChAdOx1 nCoV-19 (AZD1222) vaccine against SARS-CoV-2 lineages circulating in Brazil

Abstract

Several COVID-19 vaccines have shown good efficacy in clinical trials, but there remains uncertainty about the efficacy of vaccines against different variants. Here, we investigate the efficacy of ChAdOx1 nCoV-19 (AZD1222) against symptomatic COVID-19 in a post-hoc exploratory analysis of a Phase 3 randomised trial in Brazil (trial registration ISRCTN89951424). Nose and throat swabs were tested by PCR in symptomatic participants. Sequencing and genotyping of swabs were performed to determine the lineages of SARS-CoV-2 circulating during the study. Protection against any symptomatic COVID-19 caused by the Zeta (P.2) variant was assessed in 153 cases with vaccine efficacy (VE) of 69% (95% CI 55, 78). 49 cases of B.1.1.28 occurred and VE was 73% (46, 86). The Gamma (P.1) variant arose later in the trial and fewer cases (N = 18) were available for analysis. VE was 64% (−2, 87). ChAdOx1 nCoV-19 provided 95% protection (95% CI 61%, 99%) against hospitalisation due to COVID-19. In summary, we report that ChAdOx1 nCoV-19 protects against emerging variants in Brazil despite the presence of the spike protein mutation E484K.

Molecular variants of SARS-CoV-2: antigenic properties and current vaccine efficacy

“…The study also pointed to the maintained protection of ChAdOx1 against the Gamma variant despite a dip in efficacy compared to other variants. However, the conclusion was unpowered due to the limited cases and wide confidence interval [ 179 ]. On ChAdOx1 effectiveness against Delta variant, Bernal et al [ 145 ] estimated one dose effectiveness against the symptomatic disease of 30.7% (95CI: 25.2–35.7) and 67% (95CI: 61.3–71.8) for two doses.…”

Immune Evasive Effects of SARS-CoV-2 Variants to COVID-19 Emergency Used Vaccines

“…Approximately 14 days after the second dose, the AZD-1222 vaccine showed 66.7% efficacy against the SARS-CoV-2 prototype stain ( 71 ), 70.4% against Alpha ( 72 ), 10.4% against Beta ( 73 ), 66% against Delta ( 42 ). Although the number of cases to analyze was limited, ChAdOx1 nCoV-19 showed 64% efficacy against Gamma variant infection ( 74 ). These results indicated that the vaccine lost its protective effect against the Beta variant, but still was effective against other VOC.…”

SARS-CoV-2 and Coronavirus Disease Mitigation: Treatment Options, Vaccinations and Variants

“…Although the Pfizer-BioNTech COVID-19 vaccine provoked an immune response that attenuated the severity of the disease among those elderly patients from severe symptoms in non-vaccinated patients to mild symptoms in this vaccinated patient, there was a reduction of the vaccine efficacy against this Brazilian variant [245]. In a study that included 9433 participants who had two doses of ChAdOx1 nCoV-19/AZD1222 vaccine (University of Oxford, AstraZeneca, and the Serum Institute of India), the efficacy of the vaccine on the B.1.1.28 lineage was 73%, and this vaccine had 95% protection rate from COVID-19 hospitalization [246].…”