Summary of COVID-19 epigallocatechin gallate studies

1. Kawai et al., Effects of green tea gargling on Coronavirus Disease-2019: A multi-center randomized controlled trial

1,003 patient green tea gargling prophylaxis RCT: 67% lower hospitalization (p=0.5), 67% lower progression (p=0.5), and 1% fewer cases (p=1).
RCT 1,012 adults in Japan showing no statistically significant reduction in COVID-19 incidence with green tea gargling compared to water gargling. In the full analysis set, incidence was 5.4% in both groups. In the per-protocol set (PPS, gargling adherence ≥80%), green tea gargling showed a 23% relative risk reduction, without statistical significance. One hospitalization due to COVID-19 pneumonia occurred in the water gargling group. No adverse events related to gargling were observed. The study was open-label, which may have introduced performance bias. The study was likely underpowered, as the observed control incidence (5.4%) was lower than the assumed 7.8% used for sample size calculations. Additionally, ~64-67% of participants in both groups reported habitual green tea consumption, which may have attenuated any detectable difference between groups. Authors hypothesize that higher gargling frequency and catechin concentrations may be needed to achieve sufficient pharyngeal..
May 2026, AJPM Focus, https://www.sciencedirect.com/science/article/pii/S277306542600043X, https://c19p.org/kawai

2. Zhu et al., Efficacy and safety of 7-day aerosolized epigallocatechin-3-gallate in oncologic patients with COVID-19 pneumonia

114 patient aerosolized EGCG late treatment RCT: 38% greater improvement (p=0.002).
RCT 108 hospitalized oncologic patients with COVID-19 pneumonia showing significant benefit with aerosolized epigallocatechin-3-gallate (EGCG). The EGCG group showed significantly greater CT imaging improvement (64.8% vs 40.5%, P=0.004) and higher improvement rates for fever (OR 3.78, 95% CI 1.38-10.35) and dyspnea (OR 10.29, 95% CI 1.75-60.45).
Jan 2026, BMC Cancer, https://link.springer.com/10.1186/s12885-026-15553-x, https://c19p.org/zhu14