Association of public health interventions and COVID-19 incidence in Vietnam, January to December 2020

Quach, Ha-Linh; Nguyen, Khanh Cong; Hoang, Ngoc-Anh; Pham, Thai Quang; Tran, Duong Nhu; Le, Mai Thi Quynh; Do, Hung Thai; Vien, Chien Chinh; Phan, Lan Trong; Ngu, Nghia Duy; Tran, Tu Anh; Phung, Dinh Cong; Tran, Quang Dai; Dang, Tan Quang; Dang, Duc-Anh; Vogt, Florian

BACKGROUND: Vietnam implemented various public health interventions such as contact tracing and testing, mandatory quarantine, and lockdowns in response to COVID-19. However, the effects of these measures on the epidemic remain unclear. METHODS: We described public health interventions in relation to COVID-19 incidence. We used maximum likelihood estimations to assess containment delays (time between symptom onset and start of isolation) and multivariable regression to identify associated factors between interventions and COVID-19 incidence. We calculated effective reproductive numbers (Rt) based on transmission pairs. RESULTS: Interventions were introduced periodically in response to the epidemic. 817 (55.4%) among 1,474 COVID-19 cases were imported. Based on a serial interval of 8.72 (±5.65) days, we estimated Rt to reduce below 1 (lowest at 0.02 (95%CI 0-0.12)) during periods of strict border control and contact tracing, and to increase ahead of new clusters. The main method to detect cases shifted over time from passive notification to active case finding at immigration or in lockdown areas, with containment delays showing significant differences between modes of case detection. CONCLUSION: A combination of early, strict and consistently implemented of interventions is crucial to control COVID-19. Low-middle income countries with limited capacity can contain COVID-19 successfully using non-pharmaceutical interventions.