Originally published by 2 Minute Medicine^® (view original article). Reused on AccessMedicine with permission.

1. The ZF2001 vaccine significantly reduces the risk of contracting symptomatic coronavirus disease 2019 (COVID-19) as compared to a placebo control.

2. Those in the ZF2001 vaccine group also reported significantly lower rates of severe-to-critical COVID-19 infection as compared to the placebo group.

Evidence Rating Level: 1 (Excellent)

Study Rundown:

The ZF2001 vaccine contains a dimeric form of the receptor-binding domain of the SARS-CoV-2 spike protein. It has been demonstrated to have high efficacy in preventing infection with extremely transmissible strains of COVID-19 such as the delta and omicron variants. The ZF2001 vaccine also requires a less stringent cold-chain transport and storage protocol than previously approved vaccines. This means that it could have increased accessibility for global distribution. However, there is a gap in knowledge as to understanding its efficacy and safety profile in adults as measured during periods of high prevalence of the delta variant. The present study found that the ZF2001 vaccine has limited associated adverse events and is very effective at preventing both symptomatic and severe-to-critical COVID-19 for at least six months following full vaccination series in adults. This study was limited by factors such as having mostly Asian participants in their trial and limited recruitment of participants aged 60 years or older. Additionally, the efficacy of the vaccine against asymptomatic infections was not evaluated. Nevertheless, the findings are significant as they demonstrate that the ZF2001 vaccine is a viable alternative to preventing symptomatic and moderate-to-severe COVID-19 in adults to less stable vaccines which are currently approved for widespread use.

Click to read the study in NEJM

Relevant Reading: Effects of a Prolonged Booster Interval on Neutralization of Omicron Variant

In-Depth [randomized control trial]:

This randomized control trial was conducted at 31 clinical centers in Uzbekistan, Indonesia, Pakistan, Ecuador, and China, with 28,873 total participants. Patients who were 18 years of age or older and able to provide written, informed consent were eligible for the study. Patients who had a history of COVID-19, previous COVID-19 vaccination, or a history of congenital or acquired immune deficiency or autoimmune deficiency were excluded from the study. Patients in the study were randomized to receive either three placebo shots or three ZF2001 vaccine doses. The primary outcome measured was real-time PCR-confirmed symptomatic COVID-19 occurring at least seven days after the third dose. Outcomes in the primary analysis were assessed via Poisson regression models and according to the large-sample hypothesis of Poisson distribution. Based on the analysis, confirmed symptomatic COVID-19 was seen in 158 of the 12,625 participants in the ZF2001 group and in 580 of the 12,568 participants in the placebo group, for a vaccine efficacy of 75.7% (95% Confidence Interval [CI], 71 to 79.8). For severe-to-critical COVID-19, the vaccine efficacy was 87.6% (95% CI, 70.6 to 95.7). Death due to COVID-19 occurred in two participants in the ZF2001 group and in 12 participants in the placebo group, demonstrating a vaccine efficacy of 86.5% (95% CI, 38.9 to 98.5) against mortality. Additionally, vaccine efficacy was 76.1% (95% Ci, 70 to 81.2) against infection with the delta variant. The incidence of adverse events and serious adverse events was not significantly different between the two groups. Overall, this study demonstrates that the ZF2001 COVID-19 vaccine is effective and safe in adults for preventing symptomatic and moderate-to-severe COVID-19.

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