The data of 253 patients with COVID-19 who were hospitalised between November and December 2022 in Changde Hospital were enrolled in this study. The patients were divided into the LGLQ treatment group (100 cases), the LHQW treatment group (100 cases) and the placebo control group (53 cases), according to the treatment each group received. The inclusion criteria were as follows: ① the diagnosis of COVID-19 infection confirmed by quantitative polymerase chain reaction (qPCR) test; ② patients aged 18 years or older; ③ patients who had received more than two doses of the COVID-19 vaccine; and ④ asymptomatic patients or patients with mild symptoms at the time of hospitalisation.

The exclusion criteria were as follows: ① patients with malignant, autoimmune, liver, kidney, blood, neurological and endocrine diseases, as well as other serious diseases that may affect the patient’s participation in the trial or affect the results of the study; ② pregnant women, lactating mothers and allergic patients; ③ patients allergic to the known components of the drug; ④ patients vaccinated with less than one shot; and ⑤ patients who did not agree to participate in this study. This study was approved by the hospital’s research ethics committee, and informed consent was obtained from all the patients (ethics approval number: YX-2023-119-01). The clinical trial is registered with the number: NCT06355193.

According to the Diagnosis and Treatment Program for Novel Coronavirus Infections (Trial Ninth Edition) issued by the National Health and Wellness Commission [20], patients were categorised into four types: asymptomatic, mild, common and heavy. Asymptomatic infections were defined as confirmed cases without clinical symptoms. Mild infections were defined as upper respiratory tract infections as the main manifestations, such as sore throat, cough and fever.

All patients were isolated in accordance with the Diagnostic and Treatment Program for Novel Coronavirus Pneumonia (Trial Ninth Edition) issued by the National Health and Wellness Commission [21].

Langenlianqiao oral liquid was produced in accordance with the Hunan Provincial Medical Institutions Preparation Specification (2016 Edition), and its main ingredients were Mohanlian, Japanese ardisia herb, radix rehmanniae recens, Indigowoad root and forsythia (produced by Hunan Xinhui Pharmaceutical Co., Ltd). The prescription process of 1 L of LGLQ oral liquid was as follows: Mohanlian (500 g), Japanese ardisia herb (500 g), radix rehmanniae recens (300 g), Indigowoad root (500 g), forsythia (300 g), which is decocted twice, each time for 2 h. Following this, the decoction is combined and filtered before the filtrate is concentrated to a thick paste with a relative density of 1.20–1.25 (60℃); and 90% ethanol to 52% alcohol is added, stirred well and allowed to stand for 48 h before being filtered. Ethanol is then recovered from the filtrate to the extract with a relative density of 1.15 C, and 170 g sucrose is added. Water is then added, and the mixture is stirred, filtered, filled and sterilised. After isolating the patients, the LGLQ group took the treatment (Batch No. 220701; 10 ml/branch, 1 branch per time, three times a day) orally for 7 days.

LHQW capsules were manufactured in accordance with the Pharmacopoeia of the People’s Republic of China (2020 Edition). Its main ingredients were honeysuckle, forsythia, rhubarb, Panax quinquefolium, Chinese ephedra, patchouli, crude scaly fern, urtica dioica, rhodiola rosea, mountain plum, fritillaria and gypsum. In the LHQW group, after isolating the patients, the treatment was administered orally (batch number: A2204058H; 0.35 g/capsule, four capsules per time, three times daily) for 7 days (Fig. 1).

Flowchart of the present study

The placebo control group did not receive any drug treatment.

The observation indexes for patients included qPCR results monitoring and clinical observation indexes. During hospitalisation, the results of the qPCR were recorded. In terms of qPCR data, specimens were collected with pharyngeal swabs on admission and from the 5th day after admission, and primer pairs targeting 2019-NCoV-N and 2019-nCoV-ORF1ab were judged to be converted if they were both > 35. The clinical symptoms of the patients during hospitalisation, the duration and proportion of clinical symptoms were also observed.

The data were analysed using SPSS 27 statistical software. The Cochran formula was utilized to meticulously estimate the required sample size. This calculation was based on our assessment of the anticipated differences in the primary outcome measures between groups, while ensuring that the study had a statistical power of 80% and a significance level of 0.05 to detect actual clinical differences between groups. The randomisation was performed using a computer-generated random number table, and the allocation was concealed using sealed envelopes. The sample size was 253, with 100 patients in each of the two intervention groups and 53 patients in the placebo group. The allocation of a larger sample size to the two intervention groups, as opposed to the control group, was a deliberate decision influenced by considerations of resource optimization and cost-effectiveness. The measurement data were expressed as median (interquartile range), and comparisons between the groups were made using the Kruskal–Wallis test. Furthermore, the count data were expressed as cases (frequency/percentage) and statistically analysed using two-tailed test. All statistical analyses were based on the two-tailed hypothesis test, with α = 0.05 as the test level; P < 0.05 was considered statistically significant.