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1.
J Infect Dis ; 2021 Aug 23.
Article in English | MEDLINE | ID: covidwho-1634468

ABSTRACT

BACKGROUND: COVID-19 has caused a heavy disease burden globally, but impact of process and the timing of data collection on the accuracy of estimation of key epidemiological distributions are unclear. Since infection times are typically unobserved, there are relatively few estimates of the generation time distribution. METHODS: We developed a statistical framework to jointly estimate the generation time and incubation period from human-to-human transmission pairs, accounting for sampling biases. We applied the framework on 80 laboratory-confirmed human-to-human transmission pairs in China. We further inferred the infectiousness profile, serial interval distribution, proportions of pre-symptomatic transmission, and basic reproduction number () for COVID-19. RESULTS: The estimated mean incubation period was 4.8 days (95% confidence interval (CI), 4.1-5.6), and the mean generation time was 5.7 days (95% CI, 4.8-6.5). The estimated based on the estimated generation time was 2.2 (95% CI, 1.9-2.4). A simulation study suggested that our approach could provide unbiased estimates, and insensitive to the width of exposure windows. CONCLUSIONS: Properly accounting for the timing and process of data collection is critical to have correct estimates of generation time and incubation period. can be biased when it is derived based on serial interval as the proxy of generation time.

2.
Vaccine ; 2022.
Article in English | ScienceDirect | ID: covidwho-1634698

ABSTRACT

Vaccine hesitancy can be heightened due to increasing negative reports about vaccines. Emphasizing the social benefits of vaccination may shift individual attention from individual to social benefit of vaccination and hence promote prosocial vaccination. In six rounds of a population-based survey conducted over one major community epidemic of coronavirus disease 2019 (COVID-19) in Hong Kong from June to November 2020, we manipulated the question asking about acceptance of a COVID-19 vaccine with or without emphasizing the social benefit of vaccination against COVID-19 (prosocial priming) and monitored the changes of vaccine confidence by news media sentiment on vaccines. Population-weighted percentages of accepting COVID-19 vaccines by priming condition and vaccine confidence were compared across survey rounds. Logit regression models assessed the main effect of prosocial priming and the modification effects of vaccine confidence and perceived personal risk from COVID-19 on acceptance of COVID-19 vaccines. We found that prosocial priming significantly increased acceptance of COVID-19 vaccines across all survey rounds except for Round 3 when incidence of COVID-19 reached a peak. Vaccine confidence significantly declined in Round 6 when news media sentiment on vaccines became predominantly negative. The effect of prosocial priming on promoting vaccine acceptance was significantly greater in participants with low vaccine confidence and those perceiving the severity of COVID-19 to be mild/very mild. Our study suggests that packaging vaccination against COVID-19 as a prosocial behaviour can help overcome low vaccine confidence and promote prosocial vaccination particularly when disease incidence temporarily declines and the public perceive low severity of COVID-19.

3.
Epidemiology ; 33(1): e1, 2022 01 01.
Article in English | MEDLINE | ID: covidwho-1634716
5.
Lancet ; 2022 Jan 19.
Article in English | MEDLINE | ID: covidwho-1624570
6.
Lancet Reg Health Am ; 8: 100182, 2022 Apr.
Article in English | MEDLINE | ID: covidwho-1620909

ABSTRACT

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. Funding: US National Institutes of Health, US Centers for Disease Control and Prevention, HK Innovation and Technology Commission, China National Natural Science Foundation, European Research Council, and EPSRC Impact Acceleration Grant.

7.
Lancet ; 398(10314): 1873-1874, 2021 Nov 20.
Article in English | MEDLINE | ID: covidwho-1590364
8.
Clin Infect Dis ; 2021 Jan 06.
Article in English | MEDLINE | ID: covidwho-1599372

ABSTRACT

BACKGROUND: Disparities were marked in previous pandemics, usually with higher attack rates reported for those in lower socioeconomic positions and for ethnic minorities. METHODS: We examined characteristics of laboratory-confirmed COVID-19 cases in Hong Kong, assessed associations between incidence and population-level characteristics at the level of small geographic areas, and evaluated relations between socioeconomics and work-from-home (WFH) arrangements. RESULTS: The largest source of COVID-19 importations switched from students studying overseas in the second wave to foreign domestic helpers in the third. The local cases were mostly individuals not in formal employment (retirees and homemakers) and production workers who were unable to WFH. For every 10% increase in the proportion of population employed as executives or professionals in a given geographic region, there was an 84% (95% confidence interval (CI): 1% to 97%) reduction in the incidence of COVID-19 during the third wave. In contrast, in the first two waves, the same was associated with 3.69 times (95% CI: 1.02 to 13.33) higher incidence. Executives and professionals were more likely to implement WFH and experienced frequent changes in WFH practice, compared to production workers. CONCLUSIONS: Consistent findings on the reversed socioeconomic patterning of COVID-19 burden between infection waves in Hong Kong at both individual and population level analyses indicated that risks of infections may be related to occupations involving high exposure frequency and WFH flexibility. Contextual determinants should be taken into account in policy planning aiming at mitigating such disparities.

9.
Clin Infect Dis ; 2021 Jun 12.
Article in English | MEDLINE | ID: covidwho-1599313

ABSTRACT

Incubation period is an important parameter to inform quarantine period and to study transmission dynamics of infectious diseases. We conducted a systematic review and meta-analysis on published estimates of the incubation period distribution of COVID-19, and showed that the pooled median of the point estimates of the mean, median and 95 th percentile for incubation period are 6.3 days (range: 1.8 to 11.9 days), 5.4 days (range: 2.0 to 17.9 days) and 13.1 days (range: 3.2 to 17.8 days) respectively. Estimates of the mean and 95 th percentile of the incubation period distribution were considerably shorter before the epidemic peak in China compared to after the peak, and variation was also noticed for different choices of methodological approach in estimation. Our findings implied that corrections may be needed before directly applying estimates of incubation period into control of or further studies on emerging infectious diseases.

10.
BMJ Open ; 11(12): e055909, 2021 12 20.
Article in English | MEDLINE | ID: covidwho-1583093

ABSTRACT

OBJECTIVES: This study aims to explore the attenuated impact of reported avoidance behaviours adherence on the transmission of COVID-19 through cross-sectional surveys in Hong Kong, in order to make up for the lack of research on avoidance behaviours fatigue. DESIGN: 40 cross-sectional telephone surveys. SETTING: All districts in Hong Kong. PARTICIPANTS: 31 332 Cantonese or English-speaking participants at age of 18 years or above. METHODS: We collected data on behaviours and estimated the average effective reproduction number ([Formula: see text]) among the Hong Kong adult population during the COVID-19 epidemic wave in November-December 2020 and compared with the preceding epidemic in June-July 2020. RESULTS: We observed a reduction in adherence to voluntary avoidance behaviours due to pandemic fatigue, but continued adherence to regulated avoidance behaviours. The average [Formula: see text] during the post-work from home period was higher in November-December wave with estimated [Formula: see text] of 0.81 (95% CI: 0.75 to 0.87) compared with the June-July wave with an [Formula: see text] of 0.67 (95% CI: 0.60 to 0.75). CONCLUSIONS: The declined effectiveness of social distancing interventions in reducing COVID-19 transmission was associated with fatigue with voluntary avoidance behaviours in Hong Kong population, implying a need for the government to reinvigorate the public to maintain effective pandemic control.


Subject(s)
COVID-19 , Pandemics , Adolescent , Adult , Avoidance Learning , Cross-Sectional Studies , Fatigue/epidemiology , Fatigue/prevention & control , Hong Kong/epidemiology , Humans , SARS-CoV-2 , Surveys and Questionnaires , Telephone
11.
Emerg Infect Dis ; 28(1): 62-68, 2022 01.
Article in English | MEDLINE | ID: covidwho-1581411

ABSTRACT

To determine the effects of nonpharmaceutical interventions (NPIs) for coronavirus disease on pediatric hospitalizations for infection with respiratory viruses other than severe acute respiratory syndrome coronavirus 2, we analyzed hospital data for 2017-2021. Compared with 2017-2019, age-specific hospitalization rates associated with respiratory viruses greatly decreased in 2020, when NPIs were in place. Also when NPIs were in place, rates of hospitalization decreased among children of all ages for infection with influenza A and B viruses, respiratory syncytial virus, adenovirus, parainfluenza viruses, human metapneumovirus, and rhinovirus/enterovirus. Regression models adjusted for age and seasonality indicated that hospitalization rates for acute febrile illness/respiratory symptoms of any cause were reduced by 76% and by 85%-99% for hospitalization for infection with these viruses. NPIs in Hong Kong were clearly associated with reduced pediatric hospitalizations for respiratory viruses; implementing NPIs and reopening schools were associated with only a small increase in hospitalizations for rhinovirus/enterovirus infections.


Subject(s)
COVID-19 , Respiratory Syncytial Virus, Human , Respiratory Tract Infections , Viruses , Child , Hong Kong/epidemiology , Hospitalization , Humans , Infant , Respiratory Tract Infections/epidemiology , Respiratory Tract Infections/prevention & control , SARS-CoV-2
12.
Emerg Infect Dis ; 28(2): 407-410, 2022 Feb.
Article in English | MEDLINE | ID: covidwho-1575455

ABSTRACT

We estimated mean serial interval and superspreading potential for the Delta variant of severe acute respiratory syndrome coronavirus 2 in South Korea. Intervals were similar for the first (3.7 days) and second (3.5 days) study periods. Risk for superspreading events was also similar; 23% and 25% of cases, respectively, seeded 80% of transmissions.

13.
J R Soc Interface ; 18(185): 20210569, 2021 12.
Article in English | MEDLINE | ID: covidwho-1575238

ABSTRACT

Inferring the transmission potential of an infectious disease during low-incidence periods following epidemic waves is crucial for preparedness. In such periods, scarce data may hinder existing inference methods, blurring early-warning signals essential for discriminating between the likelihoods of resurgence versus elimination. Advanced insight into whether elevating caseloads (requiring swift community-wide interventions) or local elimination (allowing controls to be relaxed or refocussed on case-importation) might occur can separate decisive from ineffective policy. By generalizing and fusing recent approaches, we propose a novel early-warning framework that maximizes the information extracted from low-incidence data to robustly infer the chances of sustained local transmission or elimination in real time, at any scale of investigation (assuming sufficiently good surveillance). Applying this framework, we decipher hidden disease-transmission signals in prolonged low-incidence COVID-19 data from New Zealand, Hong Kong and Victoria, Australia. We uncover how timely interventions associate with averting resurgent waves, support official elimination declarations and evidence the effectiveness of the rapid, adaptive COVID-19 responses employed in these regions.


Subject(s)
COVID-19 , Communicable Diseases , Australia , Humans , New Zealand , SARS-CoV-2
14.
Adv Ther (Weinh) ; 4(10): 2100179, 2021 Oct.
Article in English | MEDLINE | ID: covidwho-1567924

ABSTRACT

[This corrects the article DOI: 10.1002/adtp.202100055.].

15.
Clin Infect Dis ; 73(11): e4305-e4311, 2021 12 06.
Article in English | MEDLINE | ID: covidwho-1560822

ABSTRACT

BACKGROUND: Nonpharmaceutical interventions (NPIs) against coronavirus disease 2019 (COVID-19) are vital to reducing transmission risks. However, the relative efficiency of social distancing against COVID-19 remains controversial, since social distancing and isolation/quarantine were implemented almost at the same time in China. METHODS: In this study, surveillance data of COVID-19 and seasonal influenza in 2018-2020 were used to quantify the relative efficiency of NPIs against COVID-19 in China, since isolation/quarantine was not used for the influenza epidemics. Given that the relative age-dependent susceptibility to influenza and COVID-19 may vary, an age-structured susceptible/infected/recovered model was built to explore the efficiency of social distancing against COVID-19 under different population susceptibility scenarios. RESULTS: The mean effective reproductive number, Rt, of COVID-19 before NPIs was 2.12 (95% confidence interval [CI], 2.02-2.21). By 11 March 2020, the overall reduction in Rt of COVID-19 was 66.1% (95% CI, 60.1-71.2%). In the epidemiological year 2019-20, influenza transmissibility was reduced by 34.6% (95% CI, 31.3-38.2%) compared with transmissibility in epidemiological year 2018-19. Under the observed contact pattern changes in China, social distancing had similar efficiency against COVID-19 in 3 different scenarios. By assuming the same efficiency of social distancing against seasonal influenza and COVID-19 transmission, isolation/quarantine and social distancing could lead to 48.1% (95% CI, 35.4-58.1%) and 34.6% (95% CI, 31.3-38.2%) reductions of the transmissibility of COVID-19, respectively. CONCLUSIONS: Though isolation/quarantine is more effective than social distancing, given that the typical basic reproductive number of COVID-19 is 2-3, isolation/quarantine alone could not contain the COVID-19 pandemic effectively in China.

16.
J Hazard Mater ; 425: 128051, 2022 03 05.
Article in English | MEDLINE | ID: covidwho-1561920

ABSTRACT

The number of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to increase worldwide, but despite extensive research, there remains significant uncertainty about the predominant routes of SARS-CoV-2 transmission. We conducted a mechanistic modeling and calculated the exposure dose and infection risk of each passenger in a two-bus COVID-19 outbreak in Hunan province, China. This outbreak originated from a single pre-symptomatic index case. Some human behavioral data related to exposure including boarding and alighting time of some passengers and seating position and mask wearing of all passengers were obtained from the available closed-circuit television images/clips and/or questionnaire survey. Least-squares fitting was performed to explore the effect of effective viral load on transmission risk, and the most likely quanta generation rate was also estimated. This study reveals the leading role of airborne SARS-CoV-2 transmission and negligible role of fomite transmission in a poorly ventilated indoor environment, highlighting the need for more targeted interventions in such environments. The quanta generation rate of the index case differed by a factor of 1.8 on the two buses and transmission occurred in the afternoon of the same day, indicating a time-varying effective viral load within a short period of five hours.


Subject(s)
Air Microbiology , COVID-19 , Fomites/virology , Motor Vehicles , SARS-CoV-2 , COVID-19/transmission , Disease Outbreaks , Humans
18.
Emerg Infect Dis ; 28(2)2021 Dec 03.
Article in English | MEDLINE | ID: covidwho-1551462

ABSTRACT

We report detection of severe acute respiratory syndrome coronavirus 2 Omicron variant (B.1.1.529) in an asymptomatic, fully vaccinated traveler in a quarantine hotel in Hong Kong, China. The Omicron variant was also detected in a fully vaccinated traveler staying in a room across the corridor from the index patient, suggesting transmission despite strict quarantine precautions.

19.
Diabetes Metab ; : 101307, 2021 Dec 01.
Article in English | MEDLINE | ID: covidwho-1549728

ABSTRACT

BACKGROUND AND OBJECTIVES: Type 2 diabetes mellitus (T2DM) patients with Coronavirus Disease 2019 (COVID-19) have poorer prognosis. Inconclusive evidence suggested dipeptidyl peptidase-4 inhibitors (DPP4i) might reduce inflammation and prevent Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) entry hence further evaluation on DPP4i is needed. METHODS: 1214 Patients with T2DM were admitted with COVID-19 between 21st January 2020 and 31st January 2021 in Hong Kong. Exposure was DPP4i use within the 90 days prior to admission for COVID-19. Assessed outcomes included clinical deterioration, clinical improvement, low viral load, positive Immunoglobulin G (IgG) antibody, hyperinflammatory syndrome, proportion of IgG antibody, clinical status and length of hospitalization. Multivariable logistic and linear regression models were performed to estimate odds ratios (OR) and their 95% confidence intervals (CI) of event outcomes and continuous outcomes, respectively. RESULTS: DPP4i users (N=107) was associated with lower odds of clinical deterioration (OR=0.71, 95%CI 0.54 to 0.93, P = 0.013), hyperinflammatory syndrome (OR=0.56, 95%CI 0.45 to 0.69, P < 0.001), invasive mechanical ventilation (OR=0.30, 95%CI 0.21 to 0.42, P < 0.001), reduced length of hospitalization (-4.82 days, 95%CI -6.80 to -2.84, P < 0.001), proportion of positive IgG antibody on day-3 (13% vs 8%, p=0.007) and day-7 (41% vs 26%, P < 0.001), despite lack of association between DPP4i use and in-hospital mortality. CONCLUSION: DPP4i use was associated with reduced odds of clinical deterioration and hyperinflammatory syndrome. Prospective studies are warranted to elucidate the role of DPP4i in T2DM and COVID-19.

20.
Sci Rep ; 11(1): 22480, 2021 11 18.
Article in English | MEDLINE | ID: covidwho-1526099

ABSTRACT

Monitoring community psychological and behavioural responses to coronavirus disease 2019 (COVID-19) is important for informing policy making and risk communication to sustain public compliance with challenging precautionary behaviours and mitigating the psychological impacts. Monthly telephone-based cross-sectional surveys in January-April 2020 and then weekly surveys from May through December 2020 were conducted to monitor changes in public risk perception of COVID-19, personal efficacy in self-protection, confidence in government's ability to control the pandemic, precautionary behaviours, perceived impact of precautionary behaviours, psychological fatigue and distress in Hong Kong, and examine their inter-relationships. While worry about contracting COVID-19 increased, personal efficacy and confidence in government declined as the community incidence of COVID-19 increased. The public maintained high compliance with most precautionary behaviours throughout but relaxed behaviours that were more challenging when disease incidence declined. Public confidence in government was persistently low throughout, of which, a lower level was associated with more psychological fatigue, lower compliance with precautionary behaviours and greater psychological distress. Perceived greater negative impact of precautionary behaviours was also associated with more psychological fatigue which in turn was associated with relaxation of precautionary behaviours. Female, younger and unemployed individuals reported greater psychological distress throughout different stages of the pandemic. Risk communication should focus on promoting confidence in self-protection and pandemic control to avoid helplessness to act when the pandemic resurges. Policy making should prioritize building public trust, enhancing support for sustaining precautionary behaviours, and helping vulnerable groups to adapt to the stress during the pandemic.


Subject(s)
Anxiety , COVID-19 , Health Behavior , Pandemics , Psychological Distress , SARS-CoV-2 , Adolescent , Adult , Age Factors , Aged , Anxiety/epidemiology , Anxiety/psychology , COVID-19/epidemiology , COVID-19/psychology , Cross-Sectional Studies , Female , Hong Kong/epidemiology , Humans , Male , Middle Aged , Sex Factors
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