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Background: The effect of nirmatrelvir-ritonavir on post-COVID-19 outcomes for individuals who are immunocompromised is understudied. We aimed to examine the association of nirmatrelvir-ritonavir with post-acute sequelae and mortality among patients who are immunocompromised and admitted to hospital with COVID-19., Methods: We did a retrospective cohort study using territory-wide electronic health records from the Hong Kong Hospital Authority and Hong Kong Department of Health. Eligible patients were adults aged 18 years or older who tested positive for SARS-CoV-2 during the study period (March 11, 2022, to Nov 9, 2023) and were admitted to hospital with COVID-19. Four exposure groups were formed based on immune status (immunocompromised or immunocompetent) and nirmatrelvir-ritonavir status (yes or no). The primary outcome was post-acute inpatient death, starting from 21 days after the positive RT-PCR date. Standardised mortality ratio weighting with doubly robust adjustment was applied to control for confounders. Cox models were used to estimate hazard ratios (HRs) for the outcomes., Findings: Between March 11, 2022, and Nov 9, 2023, there were 89 772 individuals with positive RT-PCR tests, of whom 39 923 met eligibility criteria and were included in the study cohort. 19 914 (49·9%) of 39 923 patients were female, 20 009 (50·1%) were male and the median age was 75·0 years (IQR 63·0-85·0). 846 (38·2%) of 2217 patients who were immunocompromised and 14 586 (38·7%) of 37 706 patients who were immunocompetent were prescribed nirmatrelvir-ritonavir. Among the patients who were immunocompromised, those patients who received nirmatrelvir-ritonavir had significantly lower risk of post-acute inpatient death (HR 0·58, 95% CI 0·45-0·74; p<0·0001) and hospitalisation for acute respiratory distress syndrome (0·43, 0·20-0·90; p=0·024) than those who did not. A significant negative interaction was found between immune status and nirmatrelvir-ritonavir on post-acute all-cause hospitalisation (relative excess risk due to interaction -0·84, 95% CI -1·30 to -0·37; p=0·0004)., Interpretation: Nirmatrelvir-ritonavir was associated with reduced risk of post-acute inpatient death among patients who were immunocompromised and admitted to hospital with COVID-19. However, the effectiveness of nirmatrelvir-ritonavir on post-acute hospitalisation outcomes was less pronounced in patients who were immunocompromised than in patients who were immunocompetent., Funding: Health and Medical Research Fund, Research Grants Council theme-based research schemes, and Research Grants Council Collaborative Research Fund., Competing Interests: Declarations of interests We declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Background: In many Asian jurisdictions, patients are required to obtain referrals from registered doctors before consulting physiotherapists. In contrast, countries such as the United States, the United Kingdom, and Australia have a direct access model for physiotherapists designed across different healthcare settings and under prescribed conditions. While research has demonstrated the benefits of direct access, issues remain on the appropriate policy design for direct access in the context of patient safety and organizational challenges in the implementation. Recently the policy to allow direct access in primary care context is being considered in Hong Kong. This study aims to examine the intervention design options for the policy of direct access to physiotherapists and identify corresponding implementation strategies, to inform the appropriate intervention design for direct access to physiotherapists and the implementation strategies., Methods: We adopt a systematic process for developing the design of the policy and the implementation strategies using an Implementation Mapping approach informed by Consolidated Framework for Implementation Research (CFIR). We will conduct literature reviews to understand the different aspects of policy intervention design and employ qualitative in-depth interviews and focus group discussions to understand key stakeholders' perspectives related to the direct access model. The identified barriers and facilitators associated with policy implementation of an acceptable intervention design will inform the development of an effective implementation strategy tailored to the implementation context. Our approach will involve mapping the research evidence and the subsequent findings from the stakeholders' deliberations into the CFIR domains and referencing the Expert Recommendations for Implementing Change (ERIC) to develop the acceptable intervention characteristics and the corresponding implementation strategies. These insights will be further validated in a Delphi Expert Survey, for a consensus-based approach., Discussion: This study employs a sequential mixed-method approach to explore the intervention characteristics for an acceptable intervention design in the policy formulation and the corresponding implementation strategy for direct access to physiotherapists. Integrating research insights into actionable policy recommendations and refining these recommendations in a Delphi Survey will inform the appropriate policy intervention design and implementation strategy for direct access to physiotherapy services., Competing Interests: Declarations. Ethics approval and consent to participate: This study had approval from the Survey and Behavioral Research Ethics Committee of The Chinese University of Hong Kong (SBRE-22–0054). After being informed about the study, all participants have to provide verbal or written informed consent before participating in this study. Consent for publication: Not applicable. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

While previous research examined coronavirus disease 2019 (COVID-19) antiviral-vaccine interactions through exploratory subgroup analysis, none specifically designed for examining this interaction or its impact on post-acute outcomes. This study examined the interaction between nirmatrelvir-ritonavir and complete COVID-19 vaccination on reducing the risk of post-acute outcomes among COVID-19 patients. We followed COVID-19 patients hospitalized between 11 March 2022 and 10 October 2023, until 31 October 2023 in Hong Kong. Exposure groups were based on nirmatrelvir-ritonavir usage and vaccination status (fully or not fully vaccinated). Post-acute death and all-cause rehospitalization were the study outcomes. Propensity score weighting was applied to balance covariates among exposure groups, including age, sex, Charlson Comorbidity Index, and concomitant treatments. Multiplicative and additive interactions between nirmatrelvir-ritonavir and vaccination status were assessed. A total of 50,438 COVID-19 patients were included in this study and arranged into four exposure groups. Significant additive interaction on post-acute rehospitalization was observed (relative excess risk, 0.10; 95% CI, 0.02-0.19; p -value, 0.018; attributable proportion, 0.07; 95% CI, 0.01-0.12; p -value, 0.017; synergy index, 1.26; 95% CI, 1.02-1.55; p -value, 0.032). The interaction on post-acute mortality was marginally significant. In the subgroup analysis, the interaction effect is more pronounced in older adults, female, and CoronaVac recipients. In conclusion, our study demonstrated an additive interaction between nirmatrelvir-ritonavir and complete vaccination on post-acute outcomes, suggesting greater long-term benefits of the antiviral for fully vaccinated individuals compared to not fully vaccinated patients.

Background: Studies have established the short-term efficacy of nirmatrelvir-ritonavir in managing COVID-19, yet its effect on post-COVID-19 condition, especially in patients admitted to hospital, remains understudied. This study aimed to examine the effect of nirmatrelvir-ritonavir on post-COVID-19 condition among patients admitted to hospital in Hong Kong., Methods: This retrospective cohort study used real-world, territory-wide inpatient records, vaccination records, and confirmed COVID-19 case data from the Hong Kong Hospital Authority and Department of Health, The Government of the Hong Kong Special Administrative Region. Patients aged 18 years and older who tested positive for SARS-CoV-2 between March 11, 2022, and Oct 10, 2023, and who were admitted to hospital with COVID-19 were included. The treatment group included patients prescribed nirmatrelvir-ritonavir within 5 days of symptom onset, excluding those prescribed molnupiravir within 21 days, and the control group had no exposure to either nirmatrelvir-ritonavir or molnupiravir. The outcomes were post-acute inpatient death and 13 sequelae (congestive heart failure, atrial fibrillation, coronary artery disease, deep vein thrombosis, chronic pulmonary disease, acute respiratory distress syndrome, interstitial lung disease, seizure, anxiety, post-traumatic stress disorder, end-stage renal disease, acute kidney injury, and pancreatitis). These outcomes were evaluated starting at 21 days after the positive RT-PCR date in each respective cohort constructed for the outcome. Standardised mortality ratio weights were applied to balance covariates, and Cox proportional hazards regression was used to investigate the relationship between nirmatrelvir-ritonavir and outcomes., Findings: 136 973 patients were screened for inclusion, among whom 50 055 were eligible and included in the analysis (24 873 [49·7%] were female and 25 182 [50·3%] were male). 15 242 patients were prescribed nirmatrelvir-ritonavir during acute COVID-19 and 23 756 patients were included in the control group; 11 057 patients did not meet our definition for the exposed and unexposed groups. Patients were followed up for a median of 393 days (IQR 317-489). In the nirmatrelvir-ritonavir group compared with the control group, there was a significantly lower hazard of post-acute inpatient death (hazard ratio 0·62 [95% CI 0·57-0·68]; p<0·0001), congestive heart failure (0·70 [0·58-0·85]; p=0·0002), atrial fibrillation (0·63 [0·52-0·76]; p<0·0001), coronary artery disease (0·71 [0·59-0·85]; p=0·0002), chronic pulmonary disease (0·68 [0·54-0·86]; p=0·0011), acute respiratory distress syndrome (0·71 [0·58-0·86]; p=0·0007), interstitial lung disease (0·17 [0·04-0·75]; p=0·020), and end-stage renal disease (0·37 [0·18-0·74]; p=0·0049). There was no evidence indicating difference between the groups in deep vein thrombosis, seizure, anxiety, post-traumatic stress disorder, acute kidney injury, and pancreatitis., Interpretation: This study showed extended benefits of nirmatrelvir-ritonavir for reducing the risk of post-acute inpatient death as well as cardiovascular and respiratory complications among patients admitted to hospital with COVID-19. Further research is essential to uncover the underlying mechanisms responsible for these observed negative associations and to devise effective strategies for preventing the onset of post-acute sequelae., Funding: Health and Medical Research Fund, Research Grants Council theme-based research schemes, and Research Grants Council Collaborative Research Fund., Competing Interests: Declaration of interests We declare no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.)

Background: The available evidence presented inconsistencies and inconclusive findings regarding the associations between co-existing asthma and mortality among COVID-19 patients. The objective of the current study is to investigate the relationship between asthma and severe outcomes after SARS-CoV-2 Omicron infection in an infection-naïve population., Methods: A retrospective cohort study using propensity score matching was conducted. The COVID-19 patients requiring hospitalisation in Hong Kong from January 1, 2022, to November 13, 2022, an Omicron-predominated period, were identified. Severe clinical outcomes were defined as ICU admission and inpatient death after the first positive PCR results as well as a composite outcome of both., Results: Of the 74,396 hospitalised COVID-19 patients admitted, 1,290 asthma patients and 18,641 non-asthma patients were included in the matched cohort. The rates of death and the composite outcome were 15·3% and 17·2%, respectively, among the non-asthma patients,12·2% and 13·6%, respectively, among the asthma patients, with adjusted hazard ratios equal to 0·775 (95% CI: 0·660-0·909) and 0·770 (95% CI: 0·662-0·895), respectively. The negative association was more apparent in the elderly and female groups. Asthma remained a factor that lowered the risk of disease severity even though the patients were not fully vaccinated with at least two doses., Conclusions: We used real-world data to demonstrate that asthma was not a risk factor for COVID-19 severity of the infections of Omicron variant, even though the patients were not fully vaccinated., (© 2024. The Author(s).)

Background: While many investigations examined the association between environmental covariates and COVID-19 incidence, none have examined their relationship with superspreading, a characteristic describing very few individuals disproportionally infecting a large number of people., Methods: Contact tracing data of all the laboratory-confirmed COVID-19 cases in Hong Kong from February 16, 2020 to April 30, 2021 were used to form the infection clusters for estimating the time-varying dispersion parameter (k t ), a measure of superspreading potential. Generalized additive models with identity link function were used to examine the association between negative-log k t (larger means higher superspreading potential) and the environmental covariates, adjusted with mobility metrics that account for the effect of social distancing measures., Results: A total of 6,645 clusters covering 11,717 cases were reported over the study period. After centering at the median temperature, a lower ambient temperature at 10 th percentile (18.2 °C) was significantly associated with a lower estimate of negative-log k t (adjusted expected change: -0.239 [95 % CI: -0.431 to -0.048]). While a U-shaped relationship between relative humidity and negative-log k t was observed, an inverted U-shaped relationship with actual vapour pressure was found. A higher total rainfall was significantly associated with lower estimates of negative-log k t ., Conclusions: This study demonstrated a link between meteorological factors and the superspreading potential of COVID-19. We speculated that cold weather and rainy days reduced the social activities of individuals minimizing the interaction with others and the risk of spreading the diseases in high-risk facilities or large clusters, while the extremities of relative humidity may favor the stability and survival of the SARS-CoV-2 virus., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: In 2022, SARS-CoV-2 Omicron variants circulated globally, generating concerns about increased transmissibility and immune escape. Hong Kong, having an infection-naive population with a moderate 2-dose vaccine coverage (63% by the end of 2021), experienced a COVID-19 epidemic largely seeded by Omicron BA.2 variants that led to the greatest outbreak in the region to date. Little remains known about the protection of commonly-administered vaccines against transmission of Omicron BA.2 variants., Methods: In this retrospective cohort study, we identified 17 535 laboratory-confirmed COVID-19 cases using contact tracing information during the Omicron-predominant period between January and June 2022 in Hong Kong. Demographic characteristics, time from positive test result to case reporting, isolation, or hospital admission, as well as contact tracing history and contact setting were extracted. Transmission pairs were reconstructed through suspected epidemiological links according to contact tracing history, and the number of secondary cases was determined for each index case as a measurement for risk of transmission. The effectiveness of mRNA vaccine (BNT162b2) and inactivated vaccine (Sinovac) against transmission of BA.2 variants was estimated using zero-inflated negative binomial regression models., Results: Vaccine effectiveness against transmission for patients who received the 2-dose BNT162b2 vaccine was estimated at 56.2% (95% CI: 14.5, 77.6), 30.6% (95% CI: 13.0, 44.6), and 21.3% (95% CI: 2.9, 36.2) on 15 - 90, 91 - 180, and 181 - 270 days after vaccination, respectively, showing a significant decrease over time. For 3-dose vaccines, vaccine effectiveness estimates were 41.0% (95% CI: 11.3, 60.7) and 41.9% (95% CI: 6.1, 64.0) on 15 - 180 days after booster doses of Sinovac and BNT162b2, respectively. Although significant vaccine effectiveness was detected in household settings, no evidence of such protective association was detected in non-household settings for either Sinovac or BNT162b2., Conclusion: Moderate and significant protection against Omicron BA.2 variants' transmission was found for 2 and 3 doses of Sinovac or BNT162b2 vaccines. Although protection by 2-dose BNT162b2 may evidently wane with time, protection could be restored by the booster dose. Here, we highlight the importance of continuously evaluating vaccine effectiveness against transmission for emerging SARS-CoV-2 variants., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Background: Few studies have used real-world data to evaluate the impact of antidepressant use on the risk of developing severe outcomes after SARS-CoV-2 Omicron infection., Methods: This is a retrospective cohort study using propensity-score matching to examine the relationship between antidepressant use and COVID-19 severity. Inpatient and medication records of all adult COVID-19 patients in Hong Kong during the Omicron-predominated period were obtained. Severe clinical outcomes including intensive care unit admission and inpatient death after the first positive results of reverse transcription polymerase chain reaction as well as a composite outcome of both were studied. Cox proportional hazard models were applied to estimate the crude and adjusted hazard ratios (HR)., Findings: Of 60,903 hospitalised COVID-19 patients admitted, 40,459 were included for matching, among which 3821 (9.4%) were prescribed antidepressants. The rates of intensive care unit admission, inpatient death, and the composite event were 3.9%, 25.5%, and 28.3% respectively in the unexposed group, 1.3%, 20.0%, and 21.1% respectively in the exposed group, with adjusted HR equal to 0.332 (95% CI, 0.245-0.449), 0.868 (95% CI, 0.800-0.942), and 0.786 (95% CI, 0.727-0.850) respectively. The result was generally consistent when stratified by selective serotonin reuptake inhibitors (SSRIs) and non-SSRIs. Antidepressants with functional inhibition of acid sphingomyelinase activity, specifically fluoxetine, were also negatively associated with the outcomes. The effect of antidepressants was more apparent in female and fully vaccinated COVID-19 patients., Interpretation: Antidepressant use was associated with a lower risk of severe COVID-19. The findings support the continuation of antidepressants in patients with COVID-19, and provide evidence for the treatment potential of antidepressants for severe COVID-19., Funding: This research was supported by Health and Medical Research Fund [grant numbers COVID190105, COVID19F03, INF-CUHK-1], Collaborative Research Fund of University Grants Committee [grant numbers C4139-20G], National Natural Science Foundation of China (NSFC) [71974165], and Group Research Scheme from The Chinese University of Hong Kong., Competing Interests: All authors declare no competing interests., (© 2023 The Author(s).)

Background: While many studies evaluated the reliability of digital mobility metrics as a proxy of SARS-CoV-2 transmission potential, none examined the relationship between dining-out behavior and the superspreading potential of COVID-19., Objective: We employed the mobility proxy of dining out in eateries to examine this association in Hong Kong with COVID-19 outbreaks highly characterized by superspreading events., Methods: We retrieved the illness onset date and contact-tracing history of all laboratory-confirmed cases of COVID-19 from February 16, 2020, to April 30, 2021. We estimated the time-varying reproduction number (R t ) and dispersion parameter (k), a measure of superspreading potential, and related them to the mobility proxy of dining out in eateries. We compared the relative contribution to the superspreading potential with other common proxies derived by Google LLC and Apple Inc., Results: A total of 6391 clusters involving 8375 cases were used in the estimation. A high correlation between dining-out mobility and superspreading potential was observed. Compared to other mobility proxies derived by Google and Apple, the mobility of dining-out behavior explained the highest variability of k (ΔR-sq=9.7%, 95% credible interval: 5.7% to 13.2%) and R t (ΔR-sq=15.7%, 95% credible interval: 13.6% to 17.7%)., Conclusions: We demonstrated that there was a strong link between dining-out behaviors and the superspreading potential of COVID-19. The methodological innovation suggests a further development using digital mobility proxies of dining-out patterns to generate early warnings of superspreading events., (©Ka Chun Chong, Kehang Li, Zihao Guo, Katherine Min Jia, Eman Yee Man Leung, Shi Zhao, Chi Tim Hung, Carrie Ho Kwan Yam, Tsz Yu Chow, Dong Dong, Huwen Wang, Yuchen Wei, Eng Kiong Yeoh. Originally published in JMIR Public Health and Surveillance (https://publichealth.jmir.org), 07.03.2023.)

Timely detection of an evolving event of an infectious disease with superspreading potential is imperative for territory-wide disease control as well as preventing future outbreaks. While the reproduction number (R) is a commonly-adopted metric for disease transmissibility, the transmission heterogeneity quantified by dispersion parameter k, a metric for superspreading potential is seldom tracked. In this study, we developed an estimation framework to track the time-varying risk of superspreading events (SSEs) and demonstrated the method using the three epidemic waves of COVID-19 in Hong Kong. Epidemiological contact tracing data of the confirmed COVID-19 cases from 23 January 2020 to 30 September 2021 were obtained. By applying branching process models, we jointly estimated the time-varying R and k. Individual-based outbreak simulations were conducted to compare the time-varying assessment of the superspreading potential with the typical non-time-varying estimate of k over a period of time. We found that the COVID-19 transmission in Hong Kong exhibited substantial superspreading during the initial phase of the epidemics, with only 1 % (95 % Credible interval [CrI]: 0.6-2 %), 5 % (95 % CrI: 3-7 %) and 10 % (95 % CrI: 8-14 %) of the most infectious cases generated 80 % of all transmission for the first, second and third epidemic waves, respectively. After implementing local public health interventions, R estimates dropped gradually and k estimates increased thereby reducing the risk of SSEs to approaching zero. Outbreak simulations indicated that the non-time-varying estimate of k may overlook the possibility of large outbreaks. Hence, an estimation of the time-varying k as a compliment of R as a monitoring of both disease transmissibility and superspreading potential, particularly when public health interventions were relaxed is crucial for minimizing the risk of future outbreaks., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

In January 2022, the SARS-CoV-2 Omicron variants initiated major outbreaks and dominated the transmissions in Hong Kong, displacing an earlier outbreak seeded by the Delta variants. To provide insight into the transmission potential of the emerging variants, we aimed to compare the epidemiological characteristics of the Omicron and Delta variants. We analyzed the line-list clinical and contact tracing data of the SARS-CoV-2 confirmed cases in Hong Kong. Transmission pairs were constructed based on the individual contact history. We fitted bias-controlled models to the data to estimate the serial interval, incubation period and infectiousness profile of the two variants. Viral load data were extracted and fitted to the random effect models to investigate the potential risk modifiers for the clinical viral shedding course. Totally 14 401 confirmed cases were reported between January 1 and February 15, 2022. The estimated mean serial interval (4.4 days vs. 5.8 days) and incubation period (3.4 days vs. 3.8 days) were shorter for the Omicron than the Delta variants. A larger proportion of presymptomatic transmission was observed for the Omicron (62%) compared to the Delta variants (48%). The Omicron cases had higher mean viral load over an infection course than the Delta cases, with the elder cases appearing more infectious than the younger cases for both variants. The epidemiological features of Omicron variants were likely an obstacle to contact tracing measures, imposed as a major intervention in settings like Hong Kong. Continuously monitoring the epidemiological feature for any emerging SARS-CoV-2 variants in the future is needed to assist officials in planning measures for COVID-19 control., (© 2023 The Authors. Journal of Medical Virology published by Wiley Periodicals LLC.)

Empirical evidence on the epidemiological characteristics of the emerged SARS-CoV-2 variants could shed light on the transmission potential of the virus and strategic outbreak control planning. In this study, by using contact tracing data collected during an Omicron-predominant epidemic phase in Hong Kong, we estimated the mean serial interval of SARS-CoV-2 Omicron BA.4, BA.5, and BA.2.12.1 variants at 2.8 days (95% credible interval [CrI]: 1.5, 6.7), 2.7 days (95% CrI: 2.1, 3.6), and 4.4 days (95% CrI: 2.6, 7.5), respectively, with adjustment for right truncation and sampling bias. The short serial interval for the current circulating variant indicated that outbreak mitigations through contact tracing and case isolation would be quite challenging., Competing Interests: All authors declared no conflict of interest., (© 2023 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

Importance: Few studies have evaluated the waning of vaccine effectiveness against severe outcomes caused by SARS-CoV-2 Omicron infection. Hong Kong is providing inactivated and mRNA vaccines, but the population had limited protection from natural infections before the Omicron variant emerged., Objective: To examine the change in vaccine effectiveness against hospitalization and mortality due to the Omicron variant over time., Design, Setting, and Participants: This case-control study included adults with SARS-CoV-2 Omicron variant infection who died or were hospitalized in Hong Kong from January 1 to June 5, 2022 (ie, case participants), and adults with SARS-CoV-2 Omicron, sampled from the public health registry during the study period (ie, control participants), who were matched to case participants by propensity score., Exposures: Vaccination status of the individuals., Main Outcomes and Measures: Estimated vaccine effectiveness against death, death or hospitalization, and death among hospitalized patients. Vaccine effectiveness was calculated as 1 - adjusted odds ratio obtained by conditional logistic regression adjusted with covariates for each period following vaccination., Results: There were 32 823 case participants (25 546 [77.8%] ≥65 years; 16 930 [47.4%] female) and 131 328 control participants (100 041 [76.2%] ≥65 years; 66 625 [46.6%] female) in the sample analyzed for the death or hospitalization outcome. Vaccine effectiveness against death or hospitalization was maintained for at least 6 months after the second dose of both CoronaVac (74.0%; 95% CI, 71.8%-75.8%) and BNT162b2 (77.4%; 95% CI, 75.5%-79.0%) vaccines. Vaccine effectiveness against death in those aged 18 to 49 years was 86.4% (95% CI, 85.8%-87.0%) and 92.9% (95% CI, 92.6%-93.2%) for those receiving 2 doses of CoronaVac and BNT162b2, respectively, while for patients aged 80 years or older, it dropped to 61.4% (95% CI, 59.8%-63.2%) and 52.7% (95% CI, 50.2%-55.6%) for CoronaVac and BNT162b2, respectively. Nevertheless, overall vaccine effectiveness against death at 4 to 6 months after the third dose was greater than 90% for CoronaVac, BNT162b2, and the mixed vaccine schedule (eg, mixed vaccines: vaccine effectiveness, 92.2%; 95% CI, 89.2%-95.1%)., Conclusions and Relevance: While vaccines were generally estimated to be effective against severe outcomes caused by SARS-CoV-2 Omicron infection, this analysis found that protection in older patients was more likely to wane 6 months after the second dose. Hence, a booster dose is recommended for older patients to restore immunity. This is especially critical in a setting like Hong Kong, where third-dose coverage is still insufficient among older residents.

Objective: Social distancing is one of the main non-pharmaceutical interventions used in the control of the COVID-19 pandemic. This scoping review aims to synthesise research findings on the effectiveness of different types and levels of social distancing measures in the earlier stage of COVID-19 pandemic without the confounding effect of mass vaccination., Design: Scoping review., Data Sources: MEDLINE, Embase, Global Health and four other databases were searched for eligible studies on social distancing for COVID-19 published from inception of the databases to 30 September 2020., Study Selection and Data Extraction: Effectiveness studies on social distancing between individuals, school closures, workplace/business closures, public transport restrictions and partial/full lockdown were included. Non-English articles, studies in healthcare settings or not based on empirical data were excluded., Results: After screening 1638 abstracts and 8 additional articles from other sources, 41 studies were included for synthesis of findings. The review found that the outcomes of social distancing measures were mainly indicated by changes in R t , incidence and mortality, along with indirect indicators such as daily contact frequency and travel distance. There was adequate empirical evidence for the effect of social distancing at the individual level, and for partial or full lockdown at the community level. However, at the level of social settings, the evidence was moderate for school closure, and was limited for workplace/business closures as single targeted interventions. There was no evidence for a separate effect of public transport restriction., Conclusions: In the community setting, there was stronger evidence for the combined effect of different social distancing interventions than for a single intervention. As fatigue of preventive behaviours is an issue in public health agenda, future studies should analyse the risks in specific settings such as eateries and entertainment to implement and evaluate measures which are proportionate to the risk., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Contact tracing and intensive testing programs are essential for controlling the spread of COVID-19. However, conventional contact tracing is resource intensive and may not result in the tracing of all cases due to recall bias and cases not knowing the identity of some close contacts. Few studies have reported the epidemiological features of cases not identified by contact tracing ("unlinked cases") or described their potential roles in seeding community outbreaks., Objective: For this study, we characterized the role of unlinked cases in the epidemic by comparing their epidemiological profile with the linked cases; we also estimated their transmission potential across different settings., Methods: We obtained rapid surveillance data from the government, which contained the line listing of COVID-19 confirmed cases during the first three waves in Hong Kong. We compared the demographics, history of chronic illnesses, epidemiological characteristics, clinical characteristics, and outcomes of linked and unlinked cases. Transmission potentials in different settings were assessed by fitting a negative binomial distribution to the observed offspring distribution., Results: Time interval from illness onset to hospital admission was longer among unlinked cases than linked cases (median 5.00 days versus 3.78 days; P<.001), with a higher proportion of cases whose condition was critical or serious (13.0% versus 8.2%; P<.001). The proportion of unlinked cases was associated with an increase in the weekly number of local cases (P=.049). Cluster transmissions from the unlinked cases were most frequently identified in household settings, followed by eateries and workplaces, with the estimated probability of cluster transmissions being around 0.4 for households and 0.1-0.3 for the latter two settings., Conclusions: The unlinked cases were positively associated with time to hospital admission, severity of infection, and epidemic size-implying a need to design and implement digital tracing methods to complement current conventional testing and tracing. To minimize the risk of cluster transmissions from unlinked cases, digital tracing approaches should be effectively applied in high-risk socioeconomic settings, and risk assessments should be conducted to review and adjust the policies., (©Ka Chun Chong, Katherine Jia, Shui Shan Lee, Chi Tim Hung, Ngai Sze Wong, Francisco Tsz Tsun Lai, Nancy Chau, Carrie Ho Kwan Yam, Tsz Yu Chow, Yuchen Wei, Zihao Guo, Eng Kiong Yeoh. Originally published in JMIR Public Health and Surveillance (https://publichealth.jmir.org), 16.11.2021.)

Background: The elderly healthcare voucher (EHCV) scheme is expected to lead to an increase in the number of elderly people selecting private primary healthcare services and reduce reliance on the public sector in Hong Kong. However, studies thus far have reported that this scheme has not received satisfactory responses. In this study, we examined changes in the ratio of visits between public and private doctors in primary care (to measure reliance on the public sector) for different strategic scenarios in the EHCV scheme., Methods: Based on comments from an expert panel, a system dynamics model was formulated to simulate the impact of various enhanced strategies in the scheme: increasing voucher amounts, lowering the age eligibility, and designating vouchers for chronic conditions follow-up. Data and statistics for the model calibration were collected from various sources., Results: The simulation results show that the current EHCV scheme is unable to reduce the utilization of public healthcare services, as well as the ratio of visits between public and private primary care among the local aging population. When comparing three different tested scenarios, even if the increase in the annual voucher amount could be maintained at the current pace or the age eligibility can be lowered to include those aged 60 years, the impact on shifts from public-to-private utilization were insignificant. The public-to-private ratio could only be marginally reduced from 0.74 to 0.64 in the first several years. Nevertheless, introducing a chronic disease-oriented voucher could result in a significant drop of 0.50 in the public-to-private ratio during the early implementation phase. However, the effect could not be maintained for an extended period., Conclusions: Our findings will assist officials in improving the design of the EHCV scheme, within the wider context of promoting primary care among the elderly. We suggest that an additional chronic disease-oriented voucher can serve as an alternative strategy. The scheme must be redesigned to address more specific objectives or provide a separate voucher that promotes under-utilized healthcare services (e.g., preventive care), instead of services designed for unspecified reasons, which may lead to concerns regarding exploitation.

While most countries in the Western Pacific Region (WPR) had similar trajectories of COVID-19 from January to May, their implementations of non-pharmaceutical interventions (NPIs) differed by transmission stages. To offer a better understanding for an implementation of multidisciplinary policies in COVID-19 control, we compared the impact of NPIs by assessing the transmissibility and severity of COVID-19 in different phases of the epidemic during the first five months in WPR. In this study, we estimated the piecewise instantaneous reproduction number ( R t ) and the reporting delay-adjusted case-fatality ratio (dCFR) of COVID-19 in seven WPR jurisdictions: Hong Kong Special Administrative Region, Japan, Malaysia, Shanghai, Singapore, South Korea, and Taiwan. According to the results, implementing NPIs was associated with an apparent reduction of the piecewise R t in two epidemic waves in general. However, large cluster outbreaks raised the piecewise R t to a high level. We also observed relaxing the NPIs could result in an increase of R t . The estimated dCFR ranged from 0.09% to 1.59% among the jurisdictions, except in Japan where an estimate of 5.31% might be due to low testing efforts. To conclude, in conjunction with border control measures to reduce influx of imported cases which might cause local outbreaks, other NPIs including social distancing measures along with case finding by rapid tests are also necessary to prevent potential large cluster outbreaks and transmissions from undetected cases. A comparatively lower CFR may reflect the health system capacity of these jurisdictions. In order to keep track of sustained disease transmission due to resumption of economic activities, a close monitoring of disease transmissibility is recommended in the relaxation phase. The report of transmission of SARS CoV-2 to pets in Hong Kong and to mink in farm outbreaks highlight for the control of COVID-19 and emerging infectious disease, the One Health approach is critical in understanding and accounting for how human, animals and environment health are intricately connected., Competing Interests: We declare no competing interests., (© 2021 The Author(s).)

Background: Licensure and registration are the traditional approaches to ensure minimally acceptable standards of care for practice. However, due to advances in medical technology and changes in clinical practice, the knowledge and skills obtained from basic education and training may rapidly become out of date. There is no mandated, structured and ongoing mechanism to assess all doctors' competence in Hong Kong. This paper assessed doctors' perceived needs for continuous professional development, and to identify facilitators and barriers that are likely to influence the implementation of compulsory continuous professional development for maintaining professional competence and ensuring patient safety., Methods: An explanatory sequential mixed method design with two distinct interactive phases was adopted comprising a postal self-administered questionnaire survey among a random sample of 2,459 of doctors (Phase 1), followed by individual interviews of a stratified sample of 30 questionnaire respondents for the subsequent qualitative analysis (Phase 2)., Results: The majority of doctors (over 90%) agreed the importance of continuous professional development to update knowledge and skills. However, just 30.7% of non-specialists compared with 65.4% of specialists agreed it would be desirable for continuous professional development to be a requirement for renewal of licenses. A relatively higher percentage of non-specialists compared with specialists reported barriers to participation such as accessibility, availability and relevance of the content of the programmes. Facilitators for uptake included more convenient schedule and location, relevant content, and incentives for participation such as making this a pre-condition for enrolling in government-funded services., Conclusions: To address the needs of individual doctors, the spheres of practice, personal preferences and learning styles should be considered in deciding the content and processes of continuous professional development. Flexibility is also an important principle. A learning model, incentives for participation and a compliance strategy (instead of deterrence) could be effective strategy for continuous professional development., Competing Interests: The authors declare that they have no competing interests.

To incentivize private primary care utilization and reduce reliance on public healthcare services, Elderly Healthcare Voucher Scheme has been implemented to provide a voucher entitlement to entire older resident population for subsidising their purchase of unspecified primary healthcare services in the private sector. Our study assessed whether voucher usage is associated with reduced utilization of public healthcare services. We retrieved the public healthcare services utilization and voucher transaction data of a survey cohort of 551 participants, who were age eligible for the scheme since 2009, over the period 2009-2015. Our results showed that voucher usage was not associated with reduced utilization of public healthcare services and has encouraged dual utilization of public and private healthcare. It may be due to a generated supply-induced demand and price inflation. The finding suggests the voucher is specifically designed to address the health systems issues to achieve the effective policy objectives. Defining the specific services to be provided and the prices at which they should be offered based on the needs of specified populations is a fundamental design parameter which needs to be incorporated. The alternatives of whether primary care services should be expanded and provided in the public sector or purchased using supply/demand side instruments should be considered taking the context and goals of the health system into account., Competing Interests: Declaration of Competing Interest None., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Background: Vouchers are increasingly used as a demand-side subsidy to reduce financial hardship and improve quality of services. Elderly Healthcare Voucher Scheme has been introduced by the Hong Kong Government since 2009 to provide subsidy to elderly aged 65 and above to visit ten different types of private primary care providers for curative, preventive and chronic disease management. Several enhancements have been made over the past few years. This paper (as part of an evaluation study of this unique healthcare voucher scheme) aims to assess the long term impact of the voucher scheme in encouraging the use of primary care services., Methods: Two rounds of cross-sectional survey among elderly in Hong Kong were conducted in 2010 and 2016. Propensity score matching and analysis were used to compare changes in perception and usage of vouchers over time., Results: 61.5% of respondents in 2016 agreed "the scheme encourages me to use more private primary care services", a significant increase from 36.2% in 2010. Among those who agreed in 2016, the majority thought the voucher scheme would encourage them to use acute services (90.3%) in the private sector, rather than preventive care (40.3%) and chronic disease management (12.2%). Respondents also reported that their current usual choice of care was visiting "both public and private doctors" (61.9%), representing a significant increase (up from 48.4%) prior to their use of voucher., Conclusions: The voucher scheme has encouraged the use of more private care services, particularly acute services rather than disease prevention or management of chronic disease. However, there needs to be caution that the untargeted and open-ended nature of voucher scheme could result in supply-induced demand which would affect long term financial sustainability. The dual utilization of health services in both the public and private sector may also compromise continuity and quality of care. The design of the voucher needs to be more specific, targeting prevention and chronic disease management rather than unspecified care which is mainly acute and episodic in order to maximize service delivery capacity as a whole for equitable access in universal health coverage and to contribute to a sustainable financing system.