The First 100 Days of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Control in Vietnam
Phạm Quang Thái, Maia A. Rabaa, Duong Huy Luong, Dang Quang Tan, Tran Dai Quang, Ha‐Linh Quach, Ngoc-Anh Hoang Thi, Phung Cong Dinh, Ngu Duy Nghia, Trần Anh Tú, La Ngoc Quang, Tran My Phuc, Vinh Q. Chau, Khanh Cong Nguyen, Đặng Đức Anh, Trần Như Dương, Guy Thwaites, H. Rogier van Doorn, Marc Choisy, Mary Chambers, Marc Choisy, Jeremy Day, Dong Huu Khanh Trinh, Dong Thi Hoai Tam, Joseph Donovan, Du Hong Duc, Ronald B. Geskus, Ho Quang Chanh, Hien Ho Van, Huong Dang Thao, Huynh Le Anh Huy, Huynh Ngan Ha, Huynh Trung Trieu, Huynh Xuan Yen, Evelyne Kestelyn, Thomas Kesteman, Lam Anh Nguyet, Lam Minh Yen, Katrina Lawson, Le Kim Thanh, Le Nguyen Truc Nhu, Le Thanh Hoang Nhat, Le Thi Hoang Lan, Tan Le Van, Sonia Lewycka, Nguyen Bao Tran, Nguyen Minh Nguyet, Nguyen Than Ha Quyen, Nguyễn Thanh Ngọc, Nguyen Thi Han Ny, Nguyễn Thụy Thương Thương, Nguyễn Thị Huyền Trang, Nguyen Thi Kim Tuyen, Diep Nguyen, Nguyễn Thị Phương Dung, Nguyễn Thị Thanh Tâm, Nguyen Thi Thu Hong, Nguyễn Thu Trang, Vinh Chau Nguyen Van, Nguyen Xuan Truong, Ninh Thi Thanh Van, Phan Nguyen Quoc Khanh, Phung Khanh Lam, Phung Le Kim Yen, Phung Tran Huy Nhat, Maia A. Rabaa, Thuong Nguyen Thuy Thuong, Guy Thwaites, Louise Thwaites, Tran My Phuc, Tran Tan Thanh, Trần Thị Bích Ngọc, Tran Tinh Hien, Doorn H Rogier van, Nuil Jennifer van, Vinh Q. Chau, Vũ Thị Ngọc Bích, Vu Thi Ty Hang, Sophie Yacoub
Abstract
BACKGROUND: One hundred days after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was first reported in Vietnam on 23 January, 270 cases were confirmed, with no deaths. We describe the control measures used by the government and their relationship with imported and domestically acquired case numbers, with the aim of identifying the measures associated with successful SARS-CoV-2 control. METHODS: Clinical and demographic data on the first 270 SARS-CoV-2 infected cases and the timing and nature of government control measures, including numbers of tests and quarantined individuals, were analyzed. Apple and Google mobility data provided proxies for population movement. Serial intervals were calculated from 33 infector-infectee pairs and used to estimate the proportion of presymptomatic transmission events and time-varying reproduction numbers. RESULTS: A national lockdown was implemented between 1 and 22 April. Around 200 000 people were quarantined and 266 122 reverse transcription polymerase chain reaction (RT-PCR) tests conducted. Population mobility decreased progressively before lockdown. In total, 60% (163/270) of cases were imported; 43% (89/208) of resolved infections remained asymptomatic for the duration of infection. The serial interval was 3.24 days, and 27.5% (95% confidence interval [CI], 15.7%-40.0%) of transmissions occurred presymptomatically. Limited transmission amounted to a maximum reproduction number of 1.15 (95% CI, .·37-2.·36). No community transmission has been detected since 15 April. CONCLUSIONS: Vietnam has controlled SARS-CoV-2 spread through the early introduction of mass communication, meticulous contact tracing with strict quarantine, and international travel restrictions. The value of these interventions is supported by the high proportion of asymptomatic and imported cases, and evidence for substantial presymptomatic transmission.