Efficacy, safety, and immunogenicity of the DNA SARS-CoV-2 vaccine (ZyCoV-D): the interim efficacy results of a phase 3, randomised, double-blind, placebo-controlled study in India.

BACKGROUND: ZyCoV-D, a DNA-based vaccine, showed promising safety and immunogenicity in a phase 1/2 trial. We now report the interim efficacy results of phase 3 clinical trial with ZyCoV-D vaccine in India. METHODS: We conducted an interim analysis of a multicentre, double-blind, randomised, placebo-controlled phase 3 trial at 49 centres in India. Healthy participants aged at least 12 years were enrolled and randomly assigned (1:1) to receive either ZyCov-D vaccine (Cadila Healthcare; 2 mg per dose) or placebo. An interactive web response system was used for randomisation (blocks of four) of participants as well as to enrol those aged 60 years and older with or without comorbid conditions, and those aged 12-17 years. It was also used to identify 600 participants for immunogenicity (blocks of six). Participants, investigators, and outcome assessors were masked to treatment assignment. Three doses of vaccine or placebo were administered intradermally via a needle-free injection system 28 days apart. The primary outcome was the number of participants with first occurrence of symptomatic RT-PCR-positive COVID-19 28 days after the third dose, until the targeted number of cases (interim analysis n=79, full analysis n=158) have been achieved. The analysis was done in the per-protocol population, which consisted of all participants with negative baseline SARS-CoV-2 status who received three doses of vaccine or placebo. Assessment of safety and tolerability was based on the safety population, which consisted of all enrolled participants who were known to have received at least one dose of study vaccine or placebo. This trial is registered with Clinical Trial Registry India, CTRI/2021/01/030416, and is ongoing. FINDINGS: Between Jan 16, and June 23, 2021 (data cutoff), 33 194 individuals were screened, of whom 5241 did not meet screening criteria and 27 703 were enrolled and randomly assigned to receive ZyCoV-D (n=13 851) or placebo (n=13 852). Per-protocol, 81 cases were eligible and included in efficacy analysis (20 of 12 350 in the ZyCoV-D group and 61 of 12 320 in placebo group). The ZyCoV-D vaccine efficacy was found to be 66·6% (95% CI 47·6-80·7). The occurrence of solicited adverse events was similar between the treatment groups (623 [4·49%] in the ZyCoV-D group vs 620 [4·47%] in the placebo group). There were two deaths (one in each group) reported at the data cutoff, neither of which was considered related to the study treatments. INTERPRETATION: In this interim analysis, ZyCoV-D vaccine was found to be efficacious, safe, and immunogenic in a phase 3 trial. FUNDING: National Biopharma Mission, Department of Biotechnology, Government of India and Cadila Healthcare, Ahmedabad, Gujarat India.

Safety and Immunogenicity of a DNA SARS-CoV-2 vaccine (ZyCoV-D): Results of an open-label, non-randomized phase I part of phase I/II clinical study by intradermal route in healthy subjects in India.

BACKGROUND: ZyCoV-D is a DNA vaccine candidate, which comprises a plasmid DNA carrying spike-S gene of SARS-CoV-2 virus along with gene coding for signal peptide. The spike(S) region includes the receptor-binding domain (RBD), which binds to the human angiotensin converting Enzyme (ACE)-2 receptor and mediates the entry of virus inside the cell. METHODS: We conducted a single-center, open-label, non-randomized, Phase 1 trial in India between July 2020 and October 2020. Healthy adults aged between 18 and 55 years were sequentially enrolled and allocated to one of four treatment arms in a dose escalation manner. Three doses of vaccine were administered 28 days apart and each subject was followed up for 28 days post third dose to evaluate safety and immunogenicity. FINDINGS: Out of 126 individuals screened for eligibility. Forty-eight subjects (mean age 34·9 years) were enrolled and vaccinated in the Phase 1 study Overall, 12/48 (25%) subjects reported at least one AE (i.e. combined solicited and unsolicited) during the study. There were no deaths or serious adverse events reported in Phase 1 of the study. The proportion of subjects who seroconverted based on IgG titers on day 84 was 4/11 (36·36%), 4/12 (33·33%), 10/10 (100·00%) and 8/10 (80·00%) in the treatment Arm 1 (1 mg: Needle), Arm 2 (1 mg: NFIS), Arm 3 (2 mg: Needle) and Arm 4 (2 mg: NFIS), respectively. INTERPRETATION: ZyCoV-D vaccine is found to be safe, well-tolerated and immunogenic in the Phase 1 trial. Our findings suggest that the DNA vaccine warrants further investigation.