Displaying all 6 publications

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  1. Jin S, Lim JT, Dickens BL, Cook AR
    IJID Reg, 2023 Mar;6:135-141.
    PMID: 36466213 DOI: 10.1016/j.ijregi.2022.11.013
    BACKGROUND: The COVID-19 pandemic has led to a fall of over 70% in international travel, resulting in substantial economic damages. The impact is especially pronounced in the Asia-Pacific region, where governments have been slow to relax border restrictions.

    METHODS: A retrospective approach was used to construct notional epidemic trajectories for eight Asia-Pacific countries or regions, from June to November 2021, under hypothetical scenarios of earlier resumption of international travel and selective border reopening. The numbers of local infections and deaths over the prediction window were calculated accordingly.

    RESULTS: Had quarantine-free entry been permitted for all travellers from all the regions investigated, and travel volumes recovered to the 2019 levels, Australia, New Zealand, and Singapore would have been the three most severely affected regions, with at least doubled number of deaths, while infections would have increased marginally (< 5%) for Japan, Malaysia, and Thailand.

    CONCLUSIONS: Earlier resumption of travel in Asia-Pacific, while maintaining a controlled degree of importation risk, could have been implemented through selective border-reopening strategies and on-arrival testing. Once countries had experienced large, localized COVID-19 outbreaks, earlier relaxation of border containment measures would not have resulted in a great increase in morbidity and mortality.

  2. Jin S, Lin L, Larson HJ, Cook AR
    Lancet Reg Health West Pac, 2024 Feb;43:100840.
    PMID: 38371748 DOI: 10.1016/j.lanwpc.2023.100840
    BACKGROUND: COVID-19 vaccines effectively reduced the severity of the pandemic, but the mass rollout was challenged by vaccine hesitancy, which was related to heterogenous factors-such as religiosity, mistrust, and a lack of scientific knowledge-around the globe. Distinguishing these potential influencers and quantifying their impacts would help authorities to tailor strategies that boost vaccine confidence and acceptance.

    METHODS: We conducted a large-scale, data-driven analysis on vaccine acceptance and actual uptake in eight Western Pacific countries before (2021) and after (2022) the mass COVID-19 vaccine rollouts. We compared vaccine acceptance or uptake rates between different subpopulations using Bootstrap methods and further constructed a logistic model to investigate the relationship between vaccine endorsement and diverse socio-demographic or trust-related determinants at these two time points.

    FINDINGS: Substantial between-country differences in vaccine acceptance and uptake were observed across the Western Pacific, with Mongolia, Vietnam, Laos, Cambodia, and Malaysia being more pro-vaccine than the other three countries (Japan, South Korea, and the Philippines). Actual vaccination rates in 2022 were all higher than predicted from the 2021 responses. Influencers for vaccine endorsement were country-specific, but generally, groups susceptible to vaccine hesitancy included females, the less-educated, and those distrusting vaccines or health care providers.

    INTERPRETATION: Our findings demonstrate the successful translation of vaccine intent to actual uptake with the deployment of COVID-19 vaccination in the Western Pacific. Increasing vaccine confidence and supressing dissemination of misinformation may play an essential role in reducing vaccine hesitancy and ramping up immunisation.

    FUNDING: AIR@InnoHK.

  3. Jue Tao L, Dickens BSL, Yinan M, Woon Kwak C, Ching NL, Cook AR
    J R Soc Interface, 2020 07;17(168):20200340.
    PMID: 32693746 DOI: 10.1098/rsif.2020.0340
    Dengue is hyper-endemic in Singapore and Malaysia, and daily movement rates between the two countries are consistently high, allowing inference on the role of local transmission and imported dengue cases. This paper describes a custom built sparse space-time autoregressive (SSTAR) model to infer and forecast contemporaneous and future dengue transmission patterns in Singapore and 16 administrative regions within Malaysia, taking into account connectivity and geographical adjacency between regions as well as climatic factors. A modification to forecast impulse responses is developed for the case of the SSTAR and is used to simulate changes in dengue transmission in neighbouring regions following a disturbance. The results indicate that there are long-term responses of the neighbouring regions to shocks in a region. By computation of variable inclusion probabilities, we found that each region's own past counts were important to describe contemporaneous case counts. In 15 out of 16 regions, other regions case counts were important to describe contemporaneous case counts even after controlling for past local dengue transmissions and exogenous factors. Leave-one-region-out analysis using SSTAR showed that dengue transmission counts could be reconstructed for 13 of 16 regions' counts using external dengue transmissions compared to a climate only approach. Lastly, one to four week ahead forecasts from the SSTAR were more accurate than baseline univariate autoregressions.
  4. Lim RB, Zheng H, Yang Q, Cook AR, Chia KS, Lim WY
    BMC Public Health, 2013 Oct 26;13:1012.
    PMID: 24160733 DOI: 10.1186/1471-2458-13-1012
    BACKGROUND: The increase in life expectancy and the persistence of expectancy gaps between different social groups in the 20th century are well-described in Western developed countries, but less well documented in the newly industrialised countries of Asia. Singapore, a multiethnic island-state, has undergone a demographic and epidemiologic transition concomitant with economic development. We evaluate secular trends and differences in life expectancy by ethnicity and gender in Singapore, from independence to the present.

    METHODS: Period abridged life tables were constructed to derive the life expectancy of the Singapore population from 1965 to 2009 using data from the Department of Statistics and the Registry of Births and Deaths, Singapore.

    RESULTS: All 3 of Singapore's main ethnic groups, and both genders, experienced an increase in life expectancy at birth and at 65 years from 1965 to 2009, though at substantially different rates. Although there has been a convergence in life expectancy between Indians and Chinese, the (substantial) gap between Malays and the other two ethnic groups has remained. Females continued to have a higher life expectancy at birth and at 65 years than males throughout this period, with no evidence of convergence.

    CONCLUSIONS: Ethnic and gender differences in life expectancy persist in Singapore despite its rapid economic development. Targeted chronic disease prevention measures and health promotion activities focusing on people of Malay ethnicity and the male community may be needed to remedy this inequality.

  5. Lim JT, Dickens BSL, Chew LZX, Choo ELW, Koo JR, Aik J, et al.
    PLoS Negl Trop Dis, 2020 10;14(10):e0008719.
    PMID: 33119609 DOI: 10.1371/journal.pntd.0008719
    An estimated 105 million dengue infections occur per year across 120 countries, where traditional vector control is the primary control strategy to reduce contact between mosquito vectors and people. The ongoing sars-cov-2 pandemic has resulted in dramatic reductions in human mobility due to social distancing measures; the effects on vector-borne illnesses are not known. Here we examine the pre and post differences of dengue case counts in Malaysia, Singapore and Thailand, and estimate the effects of social distancing as a treatment effect whilst adjusting for temporal confounders. We found that social distancing is expected to lead to 4.32 additional cases per 100,000 individuals in Thailand per month, which equates to 170 more cases per month in the Bangkok province (95% CI: 100-242) and 2008 cases in the country as a whole (95% CI: 1170-2846). Social distancing policy estimates for Thailand were also found to be robust to model misspecification, and variable addition and omission. Conversely, no significant impact on dengue transmission was found in Singapore or Malaysia. Across country disparities in social distancing policy effects on reported dengue cases are reasoned to be driven by differences in workplace-residence structure, with an increase in transmission risk of arboviruses from social distancing primarily through heightened exposure to vectors in elevated time spent at residences, demonstrating the need to understand the effects of location on dengue transmission risk under novel population mixing conditions such as those under social distancing policies.
  6. Lim JT, Maung K, Tan ST, Ong SE, Lim JM, Koo JR, et al.
    PLoS Comput Biol, 2021 May;17(5):e1008959.
    PMID: 34043622 DOI: 10.1371/journal.pcbi.1008959
    Mass gathering events have been identified as high-risk environments for community transmission of coronavirus disease 2019 (COVID-19). Empirical estimates of their direct and spill-over effects however remain challenging to identify. In this study, we propose the use of a novel synthetic control framework to obtain causal estimates for direct and spill-over impacts of these events. The Sabah state elections in Malaysia were used as an example for our proposed methodology and we investigate the event's spatial and temporal impacts on COVID-19 transmission. Results indicate an estimated (i) 70.0% of COVID-19 case counts within Sabah post-state election were attributable to the election's direct effect; (ii) 64.4% of COVID-19 cases in the rest of Malaysia post-state election were attributable to the election's spill-over effects. Sensitivity analysis was further conducted by examining epidemiological pre-trends, surveillance efforts, varying synthetic control matching characteristics and spill-over specifications. We demonstrate that our estimates are not due to pre-existing epidemiological trends, surveillance efforts, and/or preventive policies. These estimates highlight the potential of mass gatherings in one region to spill-over into an outbreak of national scale. Relaxations of mass gathering restrictions must therefore be carefully considered, even in the context of low community transmission and enforcement of safe distancing guidelines.
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