Multi-dimensional epidemiology and informatics data on COVID-19 wave at the end of zero COVID policy in China.

Background: China exited strict Zero-COVID policy with a surge in Omicron variant infections in December 2022. Given China's pandemic policy and population immunity, employing Baidu Index (BDI) to analyze the evolving disease landscape and estimate the nationwide pneumonia hospitalizations in the post Zero COVID period, validated by hospital data, holds informative potential for future outbreaks. Methods: Retrospective observational analyses were conducted at the conclusion of the Zero-COVID policy, integrating internet search data alongside offline records. Methodologies employed were multidimensional, encompassing lagged Spearman correlation analysis, growth rate assessments, independent sample T-tests, Granger causality examinations, and Bayesian structural time series (BSTS) models for comprehensive data scrutiny. Results: Various diseases exhibited a notable upsurge in the BDI after the policy change, consistent with the broader trajectory of the COVID-19 pandemic. Robust connections emerged between COVID-19 and diverse health conditions, predominantly impacting the respiratory, circulatory, ophthalmological, and neurological domains. Notably, 34 diseases displayed a relatively high correlation (r > 0.5) with COVID-19. Among these, 12 exhibited a growth rate exceeding 50% post-policy transition, with myocarditis escalating by 1,708% and pneumonia by 1,332%. In these 34 diseases, causal relationships have been confirmed for 23 of them, while 28 garnered validation from hospital-based evidence. Notably, 19 diseases obtained concurrent validation from both Granger causality and hospital-based data. Finally, the BSTS models approximated approximately 4,332,655 inpatients diagnosed with pneumonia nationwide during the 2 months subsequent to the policy relaxation. Conclusion: This investigation elucidated substantial associations between COVID-19 and respiratory, circulatory, ophthalmological, and neurological disorders. The outcomes from comprehensive multi-dimensional cross-over studies notably augmented the robustness of our comprehension of COVID-19's disease spectrum, advocating for the prospective utility of internet-derived data. Our research highlights the potential of Internet behavior in predicting pandemic-related syndromes, emphasizing its importance for public health strategies, resource allocation, and preparedness for future outbreaks.

Effects of Recent Prior Dengue Infection on Risk and Severity of Subsequent SARS-CoV-2 Infection: A Retrospective Cohort Study.

Background and Aims: Elucidating whether prior dengue potentially confers cross-protection against COVID-19 is of public health importance in tropical countries at risk of overlapping dengue and COVID-19 epidemics. However, studies to date have yielded conflicting results. We aimed to assess effects of recent prior dengue infection on risk and severity of subsequent SARS-CoV-2 infection among adult Singaporeans. Methods: A retrospective cohort study including all adult Singaporeans aged ≥18 years was conducted from 1 July 2021 through 31 October 2022, when a dengue outbreak driven by the DENV3 serotype preceded subsequent waves of SARS-CoV-2 Delta/Omicron transmission in Singapore. SARS-CoV-2 and dengue infection status were classified using national registries. Cox regression models adjusted for demographics, COVID-19 vaccination status, comorbidity, and socioeconomic-status were used to assess risks and severity (hospitalization, severe illness) of SARS-CoV-2 infection occurring after previous recorded dengue infection. Results: A total of 3 366 399 individuals were included, contributing 1 399 696 530 person-days of observation. A total of 13 434 dengue infections and 1 253 520 subsequent SARS-CoV-2 infections were recorded; with an average of 94.7 days (standard deviation = 83.8) between dengue infection and SARS-CoV-2 infection. Preceding dengue infection was associated with a modest increase in risk of subsequent SARS-CoV-2 infection (adjusted hazards ratio [aHR] = 1.13; 95% confidence interval [CI], 1.08-1.17), and significantly elevated risk of subsequent COVID-19 hospitalization (aHR = 3.25; 95% CI, 2.78-3.82) and severe COVID-19 (aHR = 3.39; 95% CI, 2.29-5.03). Conclusions: Increased risk of SARS-CoV-2 infection and adverse COVID-19 outcomes were observed following preceding dengue infection in a national population-based cohort of adult Singaporeans. This observation is of significance in tropical countries with overlapping dengue and COVID-19 outbreaks.

Hospitalised patients as stewards of their own antibiotic therapy: a qualitative analysis informing the strategic design of interventions to encourage shared decision-making in tertiary hospital settings in Singapore.

Background: Shared decision-making (SDM) on antibiotic therapy may improve antibiotic use in tertiary hospitals, but hospitalised patients are apprehensive about being involved in it. Understanding the facilitators and barriers to SDM can inform the design and implementation of interventions to empower these patients to engage in SDM on their antibiotic therapies. Methods: We conducted qualitative interviews with 23 adult patients purposively sampled with maximum variation from the three largest tertiary-care hospitals in Singapore (April 2019─October 2020). Thematic analysis was conducted using the Theoretical Domains Framework and Capability, Opportunity, Motivation, Behaviour (COM-B) model to identify areas for intervention. Results: Hospitalised patients lacked comprehensive knowledge of their antibiotic therapies and the majority did not have the skills to actively query their doctors about them. There was a lack of opportunities to meet and interact with doctors, and patients were less motivated to engage in SDM if they had a self-perceived paternalistic relationship with doctors, trusted their doctors to provide the best treatment, and had self-perceived poor knowledge to engage in SDM. To empower these patients, they should first be educated with antibiotic knowledge. Highlighting potential side effects of antibiotics could motivate them to ask questions about their antibiotic therapies. Environment restructuring, as facilitated by nurses and visual cues to nudge conversations, could create opportunities for interactions and motivating patients into SDM on their antibiotic therapies. Conclusion: Education and environmental restructuring should be explored to empower hospitalised patients to engage in SDM on their antibiotic therapies.

Autoimmune Sequelae After Delta or Omicron Variant SARS-CoV-2 Infection in a Highly Vaccinated Cohort.

Importance: Studies have reported increased risk of autoimmune sequelae after SARS-CoV-2 infection. However, risk may potentially be attenuated by milder Omicron (B.1.1.529) variant infection and availability of booster vaccination. Objective: To estimate the 300-day risk of new-incident autoimmune sequelae after SARS-CoV-2 Delta or Omicron BA.1 or BA.2 variant infection in adults who received COVID-19 vaccines and boosters, compared with a contemporary control group without infection. Design, Setting, and Participants: This cohort study in Singapore enrolled adults from September 1, 2021, to March 7, 2022, and followed up for 300 days. Participants were adults aged 18 years or older with SARS-CoV-2 infection during the predominance of the Delta and Omicron BA.1 or BA.2 variants and were still alive at 30 days after COVID-19 diagnosis. Exposure: The national SARS-CoV-2 testing registry was used to construct cohorts of adults with SARS-CoV-2 Delta or Omicron BA.1 or BA.2 variant infection (hereafter, cases) and a contemporaneous group with negative polymerase chain reaction or rapid antigen test results (hereafter, controls). Main Outcomes and Measures: New-incident autoimmune diagnoses after SARS-CoV-2 infection. This information was recorded in the MediClaims national health care claims database and identified 31 to 300 days after index date of infection. Risks and excess burdens were estimated using Cox proportional hazards regression model with overlap weights applied. Results: In total, 1 766 036 adults (915 096 females [51.9%]; mean [SD] age, 49 [18] years) were included in the study population, with 480 082 (27.2%) categorized as cases and 1 285 954 (72.8%) as controls. Of these adults, 73.1% had Chinese, 13.7% Malay, and 9.9% Indian ethnicity. There were 104 179 cases and 666 575 controls included during the Delta variant-predominance transmission, while 375 903 cases and 619 379 controls were included during the Omicron variant-predominance transmission. During the Delta variant period, 81.1% of cases had completed primary vaccination; during the Omicron variant period, 74.6% of cases received boosters. No significantly elevated risk of 12 prespecified autoimmune sequelae was recorded across the Omicron and Delta variant cohorts. Elevated risks of inflammatory bowel disease (adjusted hazard ratio [AHR], 2.23; 95% CI, 1.45-3.46; P < .001) and bullous skin disorders (AHR, 4.88; 95% CI, 2.47-9.66; P < .001) were observed only in the subset of COVID-19 cases requiring hospitalization during the predominance of the Omicron variant. While elevated risk of vasculitis (AHR, 5.74; 95% CI, 1.48-22.23; P = .01) was observed in vaccine-breakthrough Omicron variant infections, no increased risk of vasculitis was observed in the corresponding subgroup who received boosters. Conclusions and Relevance: This cohort study observed no significantly elevated long-term risk of autoimmune sequelae after SARS-CoV-2 Delta and Omicron BA.1 or BA.2 variant infection, except for a modestly increased risk of inflammatory bowel disease and bullous skin disorders in the hospitalized subgroup during the predominance of the Omicron variant. Booster vaccination appeared to mitigate the risk of long-term autoimmune sequelae.

Nirmatrelvir/ritonavir treatment and risk for post-acute sequelae of COVID-19 in older Singaporeans.

OBJECTIVES: Significant heterogeneity has been reported in cohort studies evaluating the impact of early oral antiviral treatment on preventing post-acute sequelae after COVID-19 (PASC). We evaluated the impact of early nirmatrelvir/ritonavir on risk of post-acute cardiovascular, neurological, respiratory and autoimmune diagnoses, as well as post-acute symptoms amongst older Singaporeans. METHODS: National COVID-19 registries and healthcare claims databases were utilized to construct a retrospective population-based cohort enrolling all Singaporeans aged≥60 years diagnosed with SARS-CoV-2 infection at primary care during Omicron transmission (18th March 2022-4th August 2023). The cohort was divided into nirmatrelvir/ritonavir-treated and untreated groups. Between-group differences in baseline characteristics were adjusted using overlap weighting. Risks of post-acute cardiovascular, neurological, respiratory and autoimmune diagnoses and post-acute symptoms (31-180 days) following SARS-CoV-2 infection were contrasted in treated/untreated groups using competing-risks regressions (adjusted for demographics/vaccination status/comorbidities). RESULTS: 188,532 older Singaporeans were included; 5.8% (10,905/188,532) received nirmatrelvir/ritonavir. No significantly decreased risk of post-acute sequelae (any sequelae: adjusted-hazards-ratio, aHR=1.06[0.94-1.19]; cardiovascular sequelae: aHR=1.01 [0.83-1.24]; neurological sequelae: aHR=1.09 [0.95-1.27]; respiratory sequelae: aHR=1.14[0.84-1.55]; autoimmune sequelae: aHR=0.76[0.53-1.09] or any post-acute symptom: aHR=0.97[0.80-1.18]) was observed up to 180 days post-infection in nirmatrelvir/ritonavir-treated individuals, versus untreated cases. Across all vaccination and age subgroups, no significantly decreased risk of any post-acute diagnosis/symptom or any cardiovascular, neurological, respiratory and autoimmune complications up to 180 days post-infection was observed. CONCLUSION: Early outpatient receipt of nirmatrelvir/ritonavir did not significantly reduce risk of post-acute cardiovascular, neurological, respiratory and autoimmune sequelae or risk of post-acute symptoms in a boosted cohort of older Singaporeans.

Long-term cardiovascular, cerebrovascular, and thrombotic complications after SARS-CoV-2-Omicron infection: a retrospective cohort study.

OBJECTIVES: Evidence suggests that some COVID-19 survivors experience a wide range of post-COVID-19 sequelae; however, the majority of studies were conducted before the emergence of the milder Omicron variant. We examined the post-acute risk of new-incident cardiovascular complications after SARS-CoV-2 infection in a multi-ethnic Asian population, during Omicron predominance. METHODS: This cohort study used national testing and healthcare claims databases in Singapore to build a cohort of individuals with confirmed SARS-CoV-2 infection during Omicron BA.1/2 transmission and a contemporaneous test-negative group. Participants in both groups were followed up for a median of 300 days. We estimated risks of new-incident cardiovascular complications using doubly robust competing-risks survival analysis. Risks were reported using two measures: hazard ratio and excess burden. RESULTS: We included 375 903 test-positive, infected individuals (mean age 48 years) and 619 379 test-negative controls (mean age 47 years). The majority (97.5%, 366 593/375 903) of infected individuals had mild infection not requiring hospitalization. There was no overall increased risk of new-incident cardiovascular complications, (adjusted hazards ratio, aHR = 1.01 [0.97-1.07]) amongst COVID-19 survivors when compared against test-negatives. A modestly increased risk and excess burden of dysrhythmias amongst COVID-19 survivors (aHR = 1.09 [1.01-1.19]) was observed. Risk and burdens of new-incident cardiovascular complications predominantly accrued in hospitalized (aHR = 2.81 [2.26-3.50]) and severe COVID-19 cases (aHR = 5.52 [3.76-8.10]). DISCUSSION: No significantly increased overall risk of any cardiovascular complication was observed in the 300 days following COVID-19 infection during the Omicron-dominant period when compared against test-negatives, with the exception of a small increased occurrence of dysrhythmias.

Dengue versus COVID-19: comparing the incidence of cardiovascular, neuropsychiatric and autoimmune complications.

BACKGROUND: While persistence of chronic symptoms following dengue infection has been documented in small prospective cohorts, population-based studies are limited. The post-acute risk of new-incident multi-systemic complications following dengue infection was contrasted against that following severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a multi-ethnic adult Asian population. METHODS: National testing and healthcare claims that databases in Singapore were utilized to build a retrospective population-based adult cohort with laboratory-confirmed infection during overlapping waves of SARS-CoV-2 and dengue transmission (1 July 2021 to 31 October 2022). Risks of new-incident cardiovascular/neuropsychiatric/autoimmune complications 31-300 days of post-dengue infection, contrasted with SARS-CoV-2 infection, were estimated using Cox regression with overlap weights. Risks were reported in terms of adjusted hazard ratio (aHR) and excess burden per 1000 persons. RESULTS: 11 707 dengue-infected individuals and 1 248 326 contemporaneous coronavirus disease 2019 (COVID-19) cases were included; the majority had mild initial infection not requiring hospitalization. Amongst dengue-infected individuals, there was 21% [aHR = 1.21 (1.06-1.38)] increased risk of any sequelae, with 55% [aHR = 1.55 (1.27-1.89)] increased risk of cardiovascular sequelae. Specifically, increased risk of dysrhythmias [aHR = 1.79(1.35-2.37)], ischemic heart disease [aHR = 1.45(1.12-1.89)], other cardiac disorders [aHR = 2.21(1.54-3.16)] and thrombotic disorders [aHR = 2.55(1.50-4.35)] was noted. Elevated risk of individual neuropsychiatric sequelae, including cerebrovascular disorders [aHR = 1.49(1.09-2.13)], cognition/memory disorders [aHR = 2.13(1.55-2.93)], extrapyramidal/movement disorders [aHR = 1.98(1.33-2.94)] and anxiety disorders [aHR = 1.61(1.01-2.56)], was observed in dengue-infected individuals compared to COVID-19 cases. Elevated risks of post-acute sequelae in dengue survivors were observed when contrasted against COVID-19 survivors infected during Delta/Omicron predominance, as well as across vaccination strata. CONCLUSION: Increased risk of post-acute cardiovascular/neuropsychiatric complications was observed in dengue survivors, when contrasted against COVID-19 survivors infected during Delta/Omicron predominance.

A Nationwide Cohort Study of Delta and Omicron SARS-CoV-2 Outcomes in Vaccinated Individuals With Chronic Lung Disease.

BACKGROUND: Individuals with chronic lung disease (CLD) are more susceptible to respiratory viral infections; however, significant heterogeneity exists in the literature on CLD and COVID-19 outcomes. Data are lacking on outcomes with newer variants (eg, Omicron) and in vaccinated and boosted populations. RESEARCH QUESTION: What are the outcomes of SARS-CoV-2 infection in individuals with CLD during Delta and Omicron transmission in a highly vaccinated and boosted population-based cohort? STUDY DESIGN AND METHODS: Outcomes of Delta and Omicron SARS-CoV-2 infection in a highly vaccinated and boosted cohort of adult Singaporeans with CLD (including asthma, COPD, bronchiectasis, and pulmonary fibrosis) were contrasted against matched population control participants. Calendar time-scale Cox regressions were used to compare risk of infection, COVID-19-related hospitalizations, and severe COVID-19 disease, adjusting for sociodemographic factors and comorbidities. RESULTS: Overall, 68,782 individual patients with CLD and 534,364 matched population control participants were included. By the end of the Omicron wave, 92.7% of patients with CLD were boosted. Compared with control participants, patients with CLD showed higher risk of SARS-CoV-2 infection, COVID-19-related hospitalization, and severe COVID-19 during both the Delta wave (infection: adjusted hazards ratio [aHR], 1.22 [95% CI, 1.17-1.28]; hospitalization: aHR, 1.76 [95% CI, 1.61-1.92]; severe COVID-19: aHR, 1.75 [95% CI, 1.50-2.05]) and Omicron wave (infection: aHR, 1.15 [95% CI, 1.14-1.17]; hospitalization: aHR, 1.82 [95% CI, 1.74-1.91]; severe COVID-19: aHR, 2.39 [95% CI, 2.18-2.63]). During Omicron, significantly higher risk of infection, hospitalization, and severe COVID-19 was observed among patients with asthma (severe COVID-19: aHR, 1.31 [95% CI, 1.10-1.55]) and COPD (severe COVID-19: aHR, 1.36 [95% CI, 1.12-1.66]) compared with control participants. Severe exacerbation (requiring hospitalization) in the preceding year was associated with higher risk of poorer outcomes (Delta severe COVID-19: aHR, 9.84 [95% CI, 6.33-15.28]; Omicron severe COVID-19: aHR, 19.22 [95% CI, 15.35-24.06]). Risk was attenuated in the boosted group, with numerically lower HRs against hospitalization and severe COVID-19 in the four-dose group compared with the three-dose group. INTERPRETATION: Increased risk of COVID-19-related hospitalization and severe COVID-19 was observed among patients with CLD compared with matched population control participants during Delta and Omicron predominance. Boosting attenuated serious COVID-19 outcomes.

Intravenous fluid therapy in hospitalized adult dengue patients without shock: Impact on subsequent severe dengue and potential adverse effects.

There is a lack of evidence on the optimal administration of intravenous (IV) fluids in hospitalized adult dengue patients without compensated and hypotensive shock. This study utilized a well-established cohort of dengue patients to compare risks of progressing to severe dengue (SD) over time for patients who were administered IV fluid versus others who were not. We included adult patients (n = 4781) who were hospitalized for dengue infection from 2005 to 2008. Cases were patients who developed SD (n = 689) and controls were patients who did not up until discharge (n = 4092). We estimated the hazard ratios (HRs) and risk of SD over time between groups administered different volumes of IV fluids versus the no IV fluid comparison group using Cox models with time-dependent covariates. The doubly-robust estimation approach was used to control for the propensity of fluid administration given clinical characteristics of patients. Subgroup analyses by age, sex, and dengue warning signs before IV fluid administration were conducted. High (>2000 mL/day) IV fluids volume was associated with a higher risk of development of SD for those who had warning signs (HR: 1.77 [1.05-2.97], p: 0.0713) and for those below 55 years old (HR: 1.53 [1.04-2.25], p: 0.0713). Low (<1000 mL/day) IV fluids volume was protective against SD for patients without warning signs (HR: 0.757 [0.578-0.990], p: 0.0883), no lethargy (HR: 0.770 [0.600-0.998], p: 0.0847), and females (HR: 0.711 [0.516-0.980], p: 0.0804). Over the course of hospitalization, there were no significant differences in IV fluid administration and SD risk in most subgroups, except in those who experienced lethargy and were administered IV fluid volume or quantity. Administering high volumes of IV fluids may be associated with an increased risk of SD during hospitalization for adult dengue patients without shock. Judicious use of IV fluids as supportive therapy is warranted.

Feasibility of wastewater-based detection of emergent pandemics through a global network of airports.

Wastewater-based surveillance has been put into practice during the pandemic. Persistence of SARS-CoV-2 in faeces of infected individuals, and high volume of passengers travelling by air, make it possible to detect virus from aircraft wastewater, lending itself to the potential identification of a novel pathogen prior to clinical diagnosis. In this study, we estimated the likelihood of detecting the virus through aircraft wastewater from the probabilities of air travel, viral shedding, defecation, testing sensitivity, and sampling. We considered various hypothetical scenarios, with diverse sampling proportions of inbound flights, surveillance airports, and sources of outbreaks. Our calculations showed that the probability of detecting SARS-CoV-2 would increase exponentially against time in the early phase of the pandemic, and would be much higher if the 20 major airports in Asia, Europe, and North America cooperated to perform aircraft wastewater surveillance. We also found other contributors to early detection, including high sampling proportion of inbound flight at destination airports, small population size of the epicentre relative to the travel volume, and large volume of outbound travelers to major airports around the globe. We concluded that routine aircraft wastewater monitoring could be a feasible approach for early identification and tracking of an emerging pathogen with high faecal shedding rates, particularly when implemented through a global surveillance network of major airports.

Long-term Cardiovascular, Cerebrovascular, and Other Thrombotic Complications in COVID-19 Survivors: A Retrospective Cohort Study.

BACKGROUND: Growing evidence suggests that some coronavirus disease 2019 (COVID-19) survivors experience a wide range of long-term postacute sequelae. We examined the postacute risk and burden of new-incident cardiovascular, cerebrovascular, and other thrombotic complications after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in a highly vaccinated multiethnic Southeast Asian population, during Delta predominance. METHODS: This cohort study used national testing and healthcare claims databases in Singapore to build a cohort of individuals who had a positive SARS-CoV-2 test between 1 September and 30 November 2021 when Delta predominated community transmission. Concurrently, we constructed a test-negative control group by enrolling individuals between 13 April 2020 and 31 December 2022 with no evidence of SARS-CoV-2 infection. Participants in both groups were followed up for a median of 300 days. We estimated risks of new-incident cardiovascular, cerebrovascular, and other thrombotic complications using doubly robust competing-risks survival analysis. Risks were reported using 2 measures: hazard ratio (HR) and excess burden (EB) with 95% confidence intervals. RESULTS: We included 106 012 infected cases and 1 684 085 test-negative controls. Compared with the control group, individuals with COVID-19 exhibited increased risk (HR, 1.157 [1.069-1.252]) and excess burden (EB, 0.70 [.53-.88]) of new-incident cardiovascular and cerebrovascular complications. Risks decreased in a graded fashion for fully vaccinated (HR, 1.11 [1.02-1.22]) and boosted (HR, 1.10 [.92-1.32]) individuals. Conversely, risks and burdens of subsequent cardiovascular/cerebrovascular complications increased for hospitalized and severe COVID-19 cases (compared to nonhospitalized cases). CONCLUSIONS: Increased risks and excess burdens of new-incident cardiovascular/cerebrovascular complications were reported among infected individuals; risks can be attenuated with vaccination and boosting.

Long-term neuropsychiatric sequelae of Delta versus Omicron SARS-CoV-2 infection.

OBJECTIVES: Studies have reported increased rates of long-term neuropsychiatric sequelae after SARS-CoV-2 infection using electronic health-record (EHR) data; however, the majority were conducted before Omicron and booster rollout. We estimated the long-term risks and excess burdens of pre-specified new-incident neuropsychiatric diagnoses after Delta versus Omicron BA.1/2 infection in a highly-vaccinated and boosted cohort of adult Singaporeans. METHODS: The national SARS-CoV-2 testing registry was used to construct cohorts of Singaporean adults infected during periods of Delta and Omicron BA.1/2 predominance and a contemporaneous test-negative control group. New-incident neuropsychiatric diagnoses recorded in the national health care claims database were identified up to 300 days postinfection. Risks and excess burden were estimated using a doubly robust competing-risks survival analysis. RESULTS: 104 179 and 375 903 infected cases were assigned to Delta and Omicron cohorts and compared against test-negative controls (Delta: N = 666 575 and Omicron: N = 619 379). Elevated risk of cognition or memory disorders was consistently reported across Omicron (Adjusted hazards ratio [aHR], 1.24; 95% CI, 1.12-1.38) and Delta cohorts (aHR, 1.63; 95% CI, 1.39-1.92). Delta-variant infection was associated with an increased risk of anosmia or dysgeusia (aHR, 4.53; 95% CI, 2.78-7.41) and psychosis (aHR, 1.65; 95% CI, 1.22-2.22). By contrast, Omicron-variant infection was associated with a risk of abnormal involuntary movements (aHR, 1.93; 95% CI, 1.32-2.83). Risks of neuropsychiatric sequelae predominantly accrued in hospitalized individuals. DISCUSSIONS: A modestly increased risk of cognition and memory disorders at 300 days after SARS-CoV-2 infection was observed among adult Singaporeans infected during the Delta/Omicron BA.1/2 transmission. There was no overall increased risk of neuropsychiatric sequelae observed across other domains. Variant-specific differences were also observed in individual neuropsychiatric sequelae, including an elevated risk of anosmia or dysgeusia after Delta-variant infection.

Effectiveness of Monovalent mRNA Vaccines Against Omicron XBB Infection in Singaporean Children Younger Than 5 Years.

Importance: Literature on vaccine effectiveness of SARS-CoV-2 messenger RNA (mRNA) vaccines for children younger than 5 years is limited. Objective: To report the effectiveness of monovalent mRNA vaccines against SARS-CoV-2 infection among Singaporean children aged 1 through 4 years during a COVID-19 pandemic wave of the Omicron XBB variant. Design, Setting, and Participants: This was a population-based cohort study, conducted over a 6-month study period from October 1, 2022, through March 31, 2023, after the implementation of community vaccination among all Singaporean children aged 1 through 4 years. The study period was dominated by the Omicron XBB subvariant. Exposure: Receipt of SARS-CoV-2 mRNA vaccines. Main Outcome Measure: Vaccine effectiveness against confirmed SARS-CoV-2 infection. The adjusted incidence rate ratio for confirmed infections using Poisson regression was reported, with the reference group being those who were unvaccinated. Analyses were stratified by prior documented SARS-CoV-2 infection. Results: A total of 121 628 children (median [IQR] age, 3.1 [2.2-3.9] years; 61 925 male [50.9%]) were included in the study, contributing 21 015 956 person-days of observation. The majority of children (11 294 of 11 705 [96.5%]) received the mRNA-1273 COVID-19 vaccine (Moderna). Vaccine effectiveness against confirmed infection was 45.2% (95% CI, 24.7%-60.2%) in partially vaccinated, infection-naive children and 63.3% (95% CI, 40.6%-77.3%) in fully vaccinated, infection-naive children compared with the unvaccinated group. Among previously infected children, vaccine effectiveness against reinfections in those with at least 1 vaccine dose was estimated at 74.6% (95% CI, 38.7%-89.5%). Conclusions and Relevance: Study results suggest that completion of a primary mRNA vaccine series provided protection against SARS-CoV-2 infection in children aged 1 through 4 years. Although incidence of hospitalization and severe illness is low in this age group, there is potential benefit of vaccination in preventing infection and potential sequelae.

Effectiveness of bivalent mRNA vaccines against medically attended symptomatic SARS-CoV-2 infection and COVID-19-related hospital admission among SARS-CoV-2-naive and previously infected individuals: a retrospective cohort study.

BACKGROUND: Emergence of the SARS-CoV-2 omicron (B.1.1.529) variant with high immune evasion has led to the development and roll-out of bivalent mRNA vaccines targeting original and omicron strains. However, real-world observational data on effectiveness of bivalent vaccines are scarce. We aimed to assess the relative effectiveness of a fourth vaccine dose with the BA.1-adapted or BA.4/BA.5-adapted bivalent vaccines against medically attended symptomatic SARS-CoV-2 infection and COVID-19-related hospital admission among SARS-CoV-2-naive and previously infected individuals in Singapore. METHODS: We conducted a retrospective cohort study among Singapore residents aged 18 years and older who had received three monovalent mRNA vaccine doses and were eligible for a fourth dose. Data were collected from official databases on COVID-19 cases and vaccinations maintained by the Singapore Ministry of Health. We analysed the incidence of medically attended symptomatic SARS-CoV-2 infection and COVID-19-related hospital admission between Oct 14, 2022, and Jan 31, 2023, by previous infection status and type of fourth vaccine dose received. Inverse probability-weighted Cox regressions were used to estimate hazard ratios (HRs). FINDINGS: 2 749 819 individuals were included in the analysis. For the SARS-CoV-2-naive group, a fourth monovalent vaccine dose did not confer additional protection over three monovalent doses against symptomatic infection (HR 1·09 [95% CI 1·07-1·11]), whereas the bivalent vaccine did provide additional protection (0·18 [0·17-0·19]). Among individuals with previous infection, the HR was 0·87 (95% CI 0·84-0·91) and 0·14 (0·13-0·15) with receipt of the fourth monovalent and bivalent doses, respectively. Against COVID-19-related hospital admission, the bivalent vaccine (HR 0·12 [95% CI 0·08-0·18] in SARS-CoV-2-naive participants and 0·04 [0·01-0·15] in previously infected participants) conferred greater benefit compared with the fourth monovalent dose (0·84 [0·77-0·91] in SARS-CoV-2-naive participants and 0·85 [0·69-1·04] in previously infected participants). INTERPRETATION: A fourth dose with the bivalent vaccine was substantially more effective against medically attended symptomatic SARS-CoV-2 infection and COVID-19-related hospital admission than four monovalent doses among both SARS-CoV-2-naive and previously infected individuals. Boosters with the bivalent vaccine might be preferred in this omicron-predominant pandemic, regardless of previous infection history. FUNDING: None.

COVID-19 Severity and Waning Immunity After up to 4 mRNA Vaccine Doses in 73 608 Patients With Cancer and 621 475 Matched Controls in Singapore: A Nationwide Cohort Study.

Importance: Despite patients with cancer being at risk of poor outcomes from COVID-19, there are few published studies for vaccine efficacy in this group, with suboptimal immunogenicity and waning vaccine efficacy described in small studies being a concern. Objective: To assess the incidence rate of severe COVID-19 disease outcomes associated with the number of vaccine doses received and the waning of protection over time. Design, Setting, and Participants: A prospective multicenter observational cohort study was carried out over 2 time periods (September 15, 2021, to December 20, 2021 [delta wave], and January 20, 2022, to November 11, 2022 [omicron wave]) predominated by SARS-CoV-2 delta and omicron variants, respectively. Overall, 73 608 patients with cancer (23 217 active treatment, 50 391 cancer survivors) and 621 475 controls matched by age, sex, race and ethnicity, and socioeconomic status were included. Exposure: Vaccine doses received, from zero to 4 doses, and time elapsed since last vaccine dose. Outcomes: Competing-risk regression analyses were employed to account for competing risks of death in patients with cancer. Main outcomes were incidence rate ratios (IRRs) of COVID-19 infection, hospitalization, and severe disease (defined as requirement for supplemental oxygen, intensive care, or death). The IRRs stratified by time from last vaccine dose served as indicators of waning of vaccine effectiveness over time. Results: The mean (SD) age of actively treated patients with cancer, cancer survivors, and controls were 62.7 (14.7), 62.9 (12.6), and 61.8 (14.7) years, respectively. Of 73 608 patients with cancer, 27 170 (36.9%) were men; 60 100 (81.6%) were Chinese, 7432 (10.1%) Malay, 4597 (6.2%) Indian, and 1479 (2.0%) were of other races and ethnicities. The IRRs for the 3-dose and 4-dose vs the 2-dose group (reference) for COVID-19 hospitalization and severe disease were significantly lower during both the delta and omicron waves in cancer and control populations. The IRRs for severe disease in the 3-dose group for active treatment, cancer survivors, and controls were 0.14, 0.13, and 0.07 during the delta wave and 0.29, 0.19, and 0.21 during omicron wave, respectively. The IRRs for severe disease in the 4-dose group during the omicron wave were even lower at 0.13, 0.10 and 0.10, respectively. No waning of vaccine effectiveness against hospitalization and severe disease was seen beyond 5 months after a third dose, nor up to 5 months (the end of this study's follow-up) after a fourth dose. Conclusion: This cohort study provides evidence of the clinical effectiveness of mRNA-based vaccines against COVID-19 in patients with cancer. Longevity of immunity in preventing severe COVID-19 outcomes in actively treated patients with cancer, cancer survivors, and matched controls was observed at least 5 months after the third or fourth dose.

Third dose of BNT162b2 improves immune response in liver transplant recipients to ancestral strain but not Omicron BA.1 and XBB.

Vaccine immunogenicity in transplant recipients can be impacted by the immunosuppressive (IS) regimens they receive. While BNT162b2 vaccination has been shown to induce an immune response in liver transplant recipients (LTRs), it remains unclear how different IS regimens may affect vaccine immunogenicity after a third BNT162b2 dose in LTRs, which is especially important given the emergence of the Omicron sublineages of SARS-CoV-2. A total of 95 LTRs receiving single and multiple IS regimens were recruited and offered three doses of BNT162b2 during the study period. Blood samples were collected on days 0, 90, and 180 after the first BNT162b2 dose. At each time point, levels of anti-spike antibodies, their neutralizing activity, and specific memory B and T cell responses were assessed. LTRs receiving single IS regimens showed an absence of poor immunogenicity, while LTRs receiving multiple IS regimens showed lower levels of spike-specific antibodies and immunological memory compared to vaccinated healthy controls after two doses of BNT162b2. With a third dose of BNT162b2, spike-specific humoral, memory B, and T cell responses in LTR significantly improved against the ancestral strain of SARS-CoV-2 and were comparable to those seen in healthy controls who received only two doses of BNT162b2. However, LTRs receiving multiple IS regimens still showed poor antibody responses against Omicron sublineages BA.1 and XBB. A third dose of BNT162b2 may be beneficial in boosting antibody, memory B, and T cell responses in LTRs receiving multiple IS regimens, especially against the ancestral Wuhan strain of SARS-CoV-2. However, due to the continued vulnerability of LTRs to presently circulating Omicron variants, antiviral treatments such as medications need to be considered to prevent severe COVID-19 in these individuals.