Effect of Lianhua Qingwen capsules on the positive rate of COVID-19 close contacts: A retrospective analysis of a large-scale population-based cohort study

OBJECTIVE: Coronavirus disease 2019 (COVID-19) is still spreading worldwide. COVID-19 close contact is a key point of this epidemic. However, no medication is now available for close contact. This study aims to evaluate the beneficial effect and safety of the Lianhua Qingwen capsule (LHQW) on COVID-19 close contacts via a large, retrospective cohort study. METHODS: A total of 25,002 close contacts from 199 quarantine sites in Changchun, Jilin, who underwent medical observation, were included. The information about these close contacts were collected for further epidemiological research. Moreover, subjects were divided into an exposure group (LHQW group, oral, 4 capsules/time, t.i.d.; 18,579 subjects) and a non-exposure group (control group; 6,423 subjects). Inverse probability of treatment weighting (IPTW) with propensity score was employed to evaluate the positive rate of the SARS-CoV-2 nucleic acid test in nasal and throat swabs confirmed by polymerase chain reaction (PCR). RESULTS: A total of 22,975 subjects were included in the analysis, 17,286 cases in the LHQW group and 5,689 cases in the control group. The positive rate of nucleic acid testing in the LHQW group was 5.12%, and that in the control group was 9.70% before the adjustment of IPTW of the propensity score; the difference between the two groups was -4.58% (95% CI -5.44- -3.77%, p < 0.001). After adjusting IPTW, the positive rate of nucleic acid testing in the LHQW group and the control group was 5.10% and 9.80%, respectively; the difference between the two groups was -4.70% (95% CI -5.18- -4.23, p < 0.001). The conclusions before and after the IPTW adjustment were consistent. No test drug-related adverse reactions were observed during the study period. CONCLUSION: LHQW has a beneficial effect and safety on the close contacts of SARS-CoV-2 who are under medical observation at the quarantine sites and can be used as an optional drug for those close contacts.