Browsing by Author "Wang, Lin"

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Cost-effective proactive testing strategies during COVID-19 mass vaccination: A modelling study
(2022-04) Du, Zhanwei; Wang, Lin; Bai, Yuan; Wang, Xutong; Pandey, Abhishek; Fitzpatrick, Meagan C.; Chinazzi, Matteo; Pastore y Piontti, Ana; Hupert, Nathaniel; Lachmann, Michael; Vespignani, Alessandro; Galvani, Alison P.; Cowling, Benjamin J.; Meyers, Lauren Ancel
Background: As SARS-CoV-2 vaccines are administered worldwide, the COVID-19 pandemic continues to exact significant human and economic costs. Mass testing of unvaccinated individuals followed by isolation of positive cases can substantially mitigate risks and be tailored to local epidemiological conditions to ensure cost effectiveness. Methods: Using a multi-scale model that incorporates population-level SARS-CoV-2 transmission and individual-level viral load kinetics, we identify the optimal frequency of proactive SARS-CoV-2 testing, depending on the local transmission rate and proportion immunized. Findings: Assuming a willingness-to-pay of US$100,000 per averted year of life lost (YLL) and a price of $10 per test, the optimal strategy under a rapid transmission scenario (Re ~ 2.5) is daily testing until one third of the population is immunized and then weekly testing until half the population is immunized, combined with a 10-day isolation period of positive cases and their households. Under a low transmission scenario (Re ~ 1.2), the optimal sequence is weekly testing until the population reaches 10% partial immunity, followed by monthly testing until 20% partial immunity, and no testing thereafter. Interpretation: Mass proactive testing and case isolation is a cost effective strategy for mitigating the COVID-19 pandemic in the initial stages of the global SARS-CoV-2 vaccination campaign and in response to resurgences of vaccine-evasive variants.
COVID-19 serial interval estimates based on confirmed cases in public reports from 86 Chinese cities
(2020-04) Du, Zhanwei; Xu, Xiaoke; Wu, Ye; Wang, Lin; Cowling, Benjamin J.; Meyers, Lauren Ancel
As a novel coronavirus (COVID-19) continues to spread widely and claim lives worldwide, its transmission characteristics remain uncertain. Here, we present and analyze the serial intervals-the time period between the onset of symptoms in an index (infector) case and the onset of symptoms in a secondary (infectee) case-of 339 confirmed cases of COVID-19 identified from 264 cities in mainland China prior to February 19, 2020. Here, we provide the complete dataset in both English and Chinese to support further COVID-19 research and modeling efforts.
Effects of Proactive Social Distancing on COVID-19 Outbreaks in 58 Cities, China
(Emerging Infectious Diseases, 2020-09) Du, Zhanwei; Xu, Xiaoke; Wang, Lin; Fox, Spencer J.; Cowling, Benjamin J.; Galvani, Alison P.; Meyers, Lauren Ancel
Cities across China implemented stringent social distancing measures in early 2020 to curb coronavirus disease outbreaks. We estimated the speed with which these measures contained transmission in cities. A 1-day delay in implementing social distancing resulted in a containment delay of 2.41 (95% CI 0.97-3.86) days.
International risk of SARS-CoV-2 Omicron variant importations originating in South Africa
(2021-12) Bai, Yuan; Du, Zhanwei; Xu, Mingda; Wang, Lin; Wu, Peng; Lau, Eric H.Y.; Cowling, Benjamin J.; Meyers, Lauren Ancel
Omicron, a fast-spreading SARS-CoV-2 variant of concern reported to the World Health Organization on November 24, 2021, has raised international alarm. We estimated there is at least 50% chance that Omicron had been introduced by travelers from South Africa into all of the 30 countries studied by November 27, 2021.
International risk of the new variant COVID-19 importations originating in the United Kingdom
(2021-03) Du, Zhanwei; Wang, Lin; Yang, Bingyi; Ali, Sheikh Taslim; Tsang, Tim K.; Shan, Songwei; Wu, Peng; Lau, Eric H.Y.; Cowling, Benjamin J.; Meyers, Lauren Ancel
A fast-spreading SARS-CoV-2 variant identified in the United Kingdom in December 2020 has raised international alarm. We estimate that, in all 15 countries analyzed, there is at least a 50% chance the variant was imported by travelers from the United Kingdom by December 7th.
Pandemic fatigue impedes mitigation of COVID-19 in Hong Kong
(2021-06) Du, Zhanwei; Wang, Lin; Shan, Songwei; Lam, Dickson; Tsang, Tim; Xiao, Jingyi; Gao, Huizhi; Yang, Bingyi; Ali, Sheikh Taslim; Pei, Sen; Fung, Isaac Chun-Hai; Lau, Eric H.Y.; Liao, Qiuyan; Wu, Peng; Meyers, Lauren Ancel; Leung, Gabriel M.; Cowling, Benjamin J.
Community-wide social distancing has been a cornerstone of pandemic control prior to mass vaccinations. The extent to which pandemic fatigue is undermining adherence to such measures and accelerating transmission remains unclear. Using large-scale weekly telephone surveys and mobility data, we characterize the evolution of risk perception and protective behaviours in Hong Kong. We estimate a 1.5% to 5.5% reduction in population compliance with protective policies for the fourth wave (October 2020 to January 2021) versus the third wave (July to August 2020), inducing prolonged disease circulation with increased infections. Mathematical models incorporating population protective behaviours estimates that the fourth wave would have been 14% smaller if not for pandemic fatigue. Mitigating pandemic fatigue is essential in maintaining population protective behaviours for controlling COVID-19. The COVID-19 pandemic has caused significant health, social, and economic burden globally. In response, countries enacted public health and social measures (PHSMs), including unprecedented movement restrictions, to control transmission. This has led to loss of employment, education, exercise opportunities, and other important social and cultural activities Pandemic fatigue is a natural response to a prolonged public health crisis due to complex interplay of cultural and social factors (e.g., the risk perception of threats). Recent studies suggest the gradual emergence of pandemic fatigue in many countries as demotivation to follow recommended mitigation behaviours Hong Kong has implemented stringent social distancing measures to curb four COVID-19 epidemic waves since January 2020. Similar PHSMs were used to contain transmission and bring case numbers down to low levels in each wave, including masks in all public areas, closure of schools, bars and social venues, work at home policies, and restaurant measures. While the third wave between July and September was brought under control within 2 months, the fourth wave starting from the end of October 2020 has taken longer to bring under control and lasted at least 5 months. One of the potential reasons for the reduced impact of PHSMs on transmission in the fourth wave is pandemic fatigue.
Risk for International Importations of Variant SARS-CoV-2 Originating in the United Kingdom
(Emerging Infectious Diseases, 2021-05) Du, Zhanwei; Wang, Lin; Yang, Bingyi; Ali, Sheikh Taslim; Tsang, Tim K.; Shan, Songwei; Wu, Peng; Lau, Eric H.Y.; Cowling, Benjamin J.; Meyers, Lauren Ancel
A fast-spreading severe acute respiratory syndrome coronavirus 2 variant identified in the United Kingdom in December 2020 has raised international alarm. We analyzed data from 15 countries and estimated that the chance that this variant was imported into these countries by travelers from the United Kingdom by December 7 is >50%.
Risk for Transportation of Coronavirus Disease from Wuhan to Other Cities in China
(Emerging Infectious Diseases, 2020-05) Du, Zhanwei; Wang, Lin; Cauchemez, Simon; Xu, Xiaoke; Wang, Xianwen; Cowling, Benjamin J.; Meyers, Lauren Ancel
On January 23, 2020, China quarantined Wuhan to contain coronavirus disease (COVID-19). We estimated the probability of transportation of COVID-19 from Wuhan to 369 other cities in China before the quarantine. Expected COVID-19 risk is >50% in 130 (95% CI 89-190) cities and >99% in the 4 largest metropolitan areas.
Serial Interval of COVID-19 among Publicly Reported Confirmed Cases
(Emerging Infectious Diseases, 2020-03-19) Du, Zhanwei; Xu, Xiaoke; Wu, Ye; Wang, Lin; Cowling, Benjamin J.; Meyers, Lauren Ancel
We estimate the distribution of serial intervals for 468 confirmed cases of coronavirus disease reported in China as of February 8, 2020. The mean interval was 3.96 days (95% CI 3.53–4.39 days), SD 4.75 days (95% CI 4.46–5.07 days); 12.6% of case reports indicated presymptomatic transmission.
The risk of SARS-CoV-2 Omicron variant emergence in low and middle-income countries (LMICs)
(2022-01) Bi, Kaiming; Herrera-Diestra, Jose; Bai, Yuan; Du, Zhanwei; Wang, Lin; Gibson, Graham; Johnson-León, Maureen; Fox, Spencer J.; Meyers, Lauren Ancel
We estimated the probability of undetected emergence of the SARS-CoV-2 Omicron variant in 25 low and middle-income countries (LMICs) prior to December 5, 2021. In nine countries, the risk exceeds 50%; in Turkey, Pakistan and the Philippines, it exceeds 99%. Risks are generally lower in the Americas than Europe or Asia.