Estimating and mitigating the risk of COVID-19 epidemic rebound associated with reopening of international borders in Vietnam: a modelling study

Abstract

Background Vietnam has emerged as one of the world's leading success stories in responding to COVID-19. After a prolonged period of little to no transmission, there was an outbreak of unknown source in July, 2020, in the Da Nang region, but the outbreak was quickly suppressed. We aimed to use epidemiological, behavioural, demographic, and policy data from the COVID-19 outbreak in Da Nang to calibrate an agent-based model of COVID-19 transmission for Vietnam, and to estimate the risk of future outbreaks associated with reopening of international borders in the country. Methods For this modelling study, we used comprehensive data from June 15 to Oct 15, 2020, on testing, COVID-19 cases, and quarantine breaches within an agent-based model of SARS-CoV-2 transmission to model a COVID-19 outbreak in Da Nang in July, 2020. We applied this model to quantify the risk of future outbreaks in Vietnam in the 3 months after the reopening of international borders, under different behavioural scenarios, policy responses (ie, closure of workplaces and schools), and ongoing testing. Findings We estimated that the outbreak in Da Nang between July and August, 2020, resulted in substantial community transmission, and that higher levels of symptomatic testing could have mitigated this transmission. We estimated that the outbreak peaked on Aug 2, 2020, with an estimated 1060 active infections (95% projection interval 890–1280). If the population of Vietnam remains highly compliant with mask-wearing policies, our projections indicate that the epidemic would remain under control even if a small but steady flow of imported infections escaped quarantine into the community. However, if complacency increases and testing rates are relatively low (10% of symptomatic individuals are tested), the epidemic could rebound again, resulting in an estimated 2100 infections (95% projected interval 1050–3610) in 3 months. These outcomes could be mitigated if the behaviour of the general population responds dynamically to increases in locally acquired cases that exceed specific thresholds, but only if testing of symptomatic individuals is also increased. Interpretation The successful response to COVID-19 in Vietnam could be improved even further with higher levels of symptomatic testing. If the previous approaches are used in response to new COVID-19 outbreaks, epidemic control is possible even in the presence of low levels of imported cases. Funding Ministry of Science and Technology (Vietnam). Translation For the Vietnamese translation of the abstract see Supplementary Materials section.

Controlling COVID-19 via test-trace-quarantine

“…Covasim also supports an extensive set of interventions: nonpharmaceutical interventions, such as distancing and masks; testing interventions, such as symptomatic and asymptomatic testing, contact tracing, isolation, and quarantine; and pharmaceutical interventions, such as therapeutics and vaccines. While Covasim was originally developed to inform policy decisions in Washington State, it has since been adapted for use in more than a dozen countries, including Vietnam 38 , Australia 39 , and the United Kingdom 40 . The code is fully open-source (available from GitHub via https://covasim.org); it includes extensive documentation (available at http://docs.covasim.org), tutorials, and software tests.…”

Covasim: An agent-based model of COVID-19 dynamics and interventions

“…To date, Covasim has been used by researchers and public health officials in over a dozen countries. Covasim has been used to inform policy decisions in the United States [ 25 , 27 ], Vietnam [ 28 ], the United Kingdom [ 29 ], and Australia [ 30 ]. It has also been used for research studies in these locations [ 31 – 34 ], and well as other countries including India, Russia, Kenya, and South Africa.…”

Seroprevalence of SARS-CoV-2 Neutralizing Antibodies among Blood Donors in Ho Chi Minh City, Vietnam, August–November 2020

“…Mask use was reported at levels of 90% in early August 2020 following reports of the outbreak in Da Nang. 12 The early and aggressive response, adaptive preventive behaviors in the community, and the warm and wet climate of local settings could have helped to limit the wide spread of SARS-CoV-2 in Ho Chi Minh City. 11 , 13 The low seroprevalence rate suggests that Vietnam’s strategies during the first wave of the epidemic was effective compared with many countries in other parts of the world.…”