A phase II/III, randomized, double-blind, placebo-controlled trial to evaluate immunogenicity and safety of the Gam-COVID-Vac combined vector vaccine in the prophylactic treatment for SARS-СoV-2 infection in the United Arab Emirates

IF 2.2 Q3 IMMUNOLOGY

Vaccine: X Pub Date : 2025-08-01 DOI:10.1016/j.jvacx.2025.100698

Ahmed A.K. AlHammadi , Amna H. Alzaabi , Haneen B. Choker , Ahmed A. Ibrahim , Asma Bin Ishaq , Ahmed E. Mahboub , Reem S. Al Dhaheri , Mohamed N. Alzaabi , Timothy A. Collyns , Gehad ElGhazali , Stefan Weber , Basel K. Al-Ramadi

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Abstract

Background

Long-term efficacy and safety profiles of the various SARS-CoV-2 vaccines were investigated. Current trial aimed to assess the safety and immunogenicity of the Gam-COVID-Vac combined vector vaccine against SARS-CoV-2-induced coronavirus infection up to 6 months post vaccination.

Research design and methods

Participants ≥18 years of age with no prior SARS-COV-2 infection or vaccination were randomized on a 3:1 ratio to receive heterologous recombinant human adenovirus-vectored vaccines or placebo, respectively. Immunogenicity was determined based on quantitative IgG antibodies to viral S and N proteins, virus- neutralizing Abs (VNA), seroconversion rates, and S protein-specific CD4 and CD8 T-cell responses.

Results

A total of 990 participants were randomized on a 3:1 ratio to vaccine and placebo groups. Majority of Adverse events were mild-moderate. Two doses of vaccine induced VNA in 100 % of participants on Day 42, with geometric mean ratio (GMR) peaking at 120 days with average 24.14 (p < 0.001). Vaccine group showed a very significant GMR for quantitative IgG to S protein. Seroconversion rates were 90.0 %, 83.7 % and 78.9 % on days 42, 120 and 180 (p < 0.001 compared to placebo). A significant rise in the median of S protein-specific CD4⁺ and CD8⁺ T- lymphocytes with a robust IFN-γ response was evident after 28 days compared to baseline. Long-term follow-up demonstrated persistent and significant CD8⁺ T-cell and IFN-γ responses at 120 days (p = 0.049 and 0.039, respectively) compared to placebo.

Conclusions

Gam-COVID-Vac vaccine showed a good safety profile and induced durable humoral and cellular immune responses. The viral-specific CD8+ T-cell response was more durable following vaccination than CD4+ T cell counterpart.

Trial Registration

The trial is registered at ClinicalTrials.gov (CT.gov identifier: NCT04656613).

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在阿拉伯联合酋长国开展一项II/III期、随机、双盲、安慰剂对照试验，评估Gam-COVID-Vac联合载体疫苗预防性治疗SARS-СoV-2感染的免疫原性和安全性

研究了各种SARS-CoV-2疫苗的长期疗效和安全性。目前的试验旨在评估Gam-COVID-Vac联合载体疫苗在接种后6个月内抗sars - cov -2诱导的冠状病毒感染的安全性和免疫原性。研究设计和方法年龄≥18岁、既往未感染SARS-COV-2或未接种过SARS-COV-2疫苗的受试者按3:1的比例随机分为异源重组人腺病毒载体疫苗组和安慰剂组。免疫原性的测定是基于对病毒S和N蛋白的定量IgG抗体、病毒中和抗体（VNA）、血清转化率和S蛋白特异性CD4和CD8 t细胞反应。结果共有990名参与者按3:1的比例随机分为疫苗组和安慰剂组。大多数不良事件为轻中度。在第42天，100%的参与者接受了两剂疫苗诱导的VNA，几何平均比（GMR）在120天达到峰值，平均为24.14 (p <；0.001)。疫苗组对S蛋白定量IgG的GMR极显著。血清转换率分别为90.0%、83.7%和78.9%，分别在第42、120和180天(p <；0.001（与安慰剂相比）。与基线相比，28天后S蛋白特异性CD4+和CD8+ T-淋巴细胞的中位数显著上升，IFN-γ反应强劲。长期随访显示，与安慰剂相比，120天的CD8+ t细胞和IFN-γ反应持续且显著（p分别= 0.049和0.039）。结论gam - covid - vac疫苗具有良好的安全性，可诱导持久的体液和细胞免疫反应。接种疫苗后，病毒特异性CD8+ T细胞应答比CD4+ T细胞应答更持久。试验注册该试验在ClinicalTrials.gov （CT.gov标识符：NCT04656613）上注册。

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