The study protocol was approved by the institutional review boards of Zhongshan Hospital, Fudan University, and the trial was registered on the Chinese Clinical Trial Registry (ChiCTR2200059824). All participants provided written informed consent. Study participants were recruited among the individuals with COVID-19 hospitalized at two Fangcang shelter hospitals, from April to May 2022, in Shanghai, China. At the time of admission, individuals with COVID-19 tested positive but no symptoms (asymptomatic infection) were invited to participate in the study.

As our study is experimental in nature with no prior reference to estimate the sample size for treatment effect testing, we made our best effort to recruit eligible participants and obtain an acceptable sample size.

Eligible participants were randomized to either the ginger supplement group or the control group, and no masking was implemented in the current trial.

The ginger supplements [Fujian Longzhi Biotechnology Co., Ltd (Fujian, China)] were provided in the form of ginger powder packed individually (1.5 g/bag), participants in the ginger supplement group were asked to mix it with hot water and take it orally at the dosage one bag per time twice daily (before breakfast and lunch), the intervention continued until the participants were discharged from the hospital. The standard for hospital discharge was their throat swab test for COVID-19 reached 35 (CT value) for consecutive 2 days without major symptoms, including but not limited to sore throat, stuffy nose, fever, and cough. Both groups received the same general medical care during the hospitalization period.

The primary outcome was the length of stay before participants were recovered and discharged from hospitals, where they had repeated negative results of COVID-19 tests and were cleared of COVID-19 as judged by the physicians in charge.

Descriptive statistics are presented as means ± SDs or numbers (percentages) for numeric and categorical variables, respectively. Baseline characteristics between groups were compared using t-test or χ2 tests when appropriate. Generalized linear models were used to analyze the effect of ginger supplement adjusted for age, sex, location, chronic disease status (hypertension, diabetes, other chronic diseases), and surgical history. To examine whether the potential effects of the ginger supplement on hospitalization time were modified by other factors, we tested the interaction between sex and intervention, age and intervention, and pre-existing medical conditions (combined data of diseases status and surgical history) and intervention by adding the interaction component in our model, adjusting for aforementioned covariates. Subgroup analyses were subsequently conducted when the interaction terms were significant. All analyses were performed using SAS version 9.4 (SAS Institute Inc), and a 2-sided P value < 0.05 was considered statistically significant.

The funding source did not play any role in study design, data collection, analyses, manuscript preparation, or decision to submit the work for publication.