Global mortality associated with seasonal influenza epidemics: New burden estimates and predictors from the GLaMOR Project

Association of frailty with influenza and hospitalization due to influenza among independent older adults: a longitudinal study of Japan Gerontological Evaluation Study (JAGES)

BACKGROUND

It is unknown that whether frailty is a risk factor of influenza and the hospitalization among older adults, although it has been shown that frailty was associated with poor recovery from the hospitalization among those. We examined the association of frailty with influenza and the hospitalization and the effect by sex among independent older adults.

METHODS

We used the longitudinal data from the Japan Gerontological Evaluation Study (JAGES), performed in 2016 and 2019 and conducted in 28 municipalities in Japan. The target population comprised 77,103 persons aged ≥ 65 years who did not need assistance from the public long-term care insurance. Primary outcome measures were influenza and hospitalization due to influenza. Frailty was evaluated with the Kihon check list. We estimated the risk of influenza, the hospitalization, those risks by sex, and the interaction for frailty and sex using Poisson regression adjusting for covariates.

RESULTS

Frailty was associated with both influenza and the hospitalization among the older adults compared with nonfrail individuals after adjusting for covariates (influenza, frail: risk ratio {RR}: 1.36, 95% confidence interval {95% CI}: 1.20 - 1.53, and prefrail: RR: 1.16, 95% CI: 1.09 - 1.23; the hospitalization, frail: RR: 3.18, 95% CI: 1.84 - 5.57, and prefrail: RR: 2.13, 95% CI: 1.44 - 3.16). Male was associated with the hospitalization, but not associated with influenza compared to female (the hospitalization: RR: 1.70, 95% CI: 1.15 - 2.52 and influenza: RR: 1.01, 95% CI: 0.95 - 1.08). The interaction for frailty and sex was significant neither in influenza nor in the hospitalization.

CONCLUSION

These results suggest that frailty is a risk of influenza and the hospitalization, that risks of the hospitalization are different by sex, but that the sex difference does not cause the effect heterogeneity of frailty on the susceptibility and severity among independent older adults.

B, Wang G, Medina RA, Van Bakel H, García-Sastre A, Nelson MI, Ghedin E, Veiga ABG. Tracking the emergence of antigenic variants in influenza A virus epidemics in Brazil

Influenza A virus (IAV) circulation patterns differ in North America and South America, with influenza seasons often characterized by different subtypes and strains. However, South America is relatively undersampled considering the size of its population. To address this gap, we sequenced the complete genomes of 220 IAVs collected between 2009 and 2016 from hospitalized patients in southern Brazil. New genetic drift variants were introduced into southern Brazil each season from a global gene pool, including four H3N2 clades (3c, 3c2, 3c3, and 3c2a) and five H1N1pdm clades (clades 6, 7, 6b, 6c, and 6b1). In 2016, H1N1pdm viruses belonging to a new 6b1 clade caused a severe influenza epidemic in southern Brazil that arrived early and spread rapidly, peaking mid-autumn. Inhibition assays showed that the A/California/07/2009(H1N1) vaccine strain did not protect well against 6b1 viruses. Phylogenetically, most 6b1 sequences that circulated in southern Brazil belong to a single transmission cluster that rapidly diffused across susceptible populations, leading to the highest levels of influenza hospitalization and mortality seen since the 2009 pandemic. Continuous genomic surveillance is needed to monitor rapidly evolving IAVs for vaccine strain selection and understand their epidemiological impact in understudied regions.

The Multifaceted Role of Annexin A1 in Viral Infections

Dysregulated inflammatory responses are often correlated with disease severity during viral infections. Annexin A1 (AnxA1) is an endogenous pro-resolving protein that timely regulates inflammation by activating signaling pathways that culminate with the termination of response, clearance of pathogen and restoration of tissue homeostasis. Harnessing the pro-resolution actions of AnxA1 holds promise as a therapeutic strategy to control the severity of the clinical presentation of viral infections. In contrast, AnxA1 signaling might also be hijacked by viruses to promote pathogen survival and replication. Therefore, the role of AnxA1 during viral infections is complex and dynamic. In this review, we provide an in-depth view of the role of AnxA1 during viral infections, from pre-clinical to clinical studies. In addition, this review discusses the therapeutic potential for AnxA1 and AnxA1 mimetics in treating viral infections.

Estimation of the influenza-associated respiratory hospitalization burden using sentinel surveillance data, Lebanon, 2015-2020

Introduction

Influenza epidemics cause around 3 to 5 million cases of severe illness worldwide every year. Estimates are needed for a better understanding of the burden of disease especially in low- and middle-income countries. The objective of this study is to estimate the number and rate of influenza-associated respiratory hospitalizations in Lebanon during five influenza seasons (2015-2016 to 2019-2020) by age and province of residence in addition to estimating the influenza burden by level of severity.

Methods

The severe acute respiratory infection sentinel surveillance system was used to compute influenza positivity from the influenza laboratory confirmed cases. The total of respiratory hospitalizations under the influenza and pneumonia diagnosis was retrieved from the Ministry of Public Health hospital billing database. Age-specific and province-specific frequencies and rates were estimated for each season. Rates per 100 000 population were calculated with 95% confidence levels.

Results

The estimated seasonal average of influenza-associated hospital admission was 2866 for a rate of 48.1 (95% CI: 46.4-49.9) per 100 000. As for the distribution by age group, the highest rates were seen in the two age groups ≥65 years and 0-4 years whereas the lowest rate was for the age group 15-49 years. For the distribution by province of residence, the highest influenza-associated hospitalization rates were reported from the Bekaa-Baalback/Hermel provinces.

Conclusion

This study shows the substantial burden of influenza in Lebanon mainly on high-risk groups (≥65 years and <5 years). It is crucial to translate these findings into policies and practices to reduce the burden and estimate the illness-related expenditure and indirect costs.

Do pathogens always evolve to be less virulent? The virulence–transmission trade-off in light of the COVID-19 pandemic

The direction the evolution of virulence takes in connection with any pathogen is a long-standing question. Formerly, it was theorized that pathogens should always evolve to be less virulent. As observations were not in line with this theoretical outcome, new theories emerged, chief among them the transmission–virulence trade-off hypotheses, which predicts an intermediate level of virulence as the endpoint of evolution. At the moment, we are very much interested in the future evolution of COVID-19’s virulence. Here, we show that the disease does not fulfill all the assumptions of the hypothesis. In the case of COVID-19, a higher viral load does not mean a higher risk of death; immunity is not long-lasting; other hosts can act as reservoirs for the virus; and death as a consequence of viral infection does not shorten the infectious period. Consequently, we cannot predict the short- or long-term evolution of the virulence of COVID-19.

IgG N-glycan Signatures as Potential Diagnostic and Prognostic Biomarkers

IgG N-glycans are an emerging source of disease-specific biomarkers. Over the last decade, the continued development of glycomic databases and the evolution of glyco-analytic methods have resulted in increased throughput, resolution, and sensitivity. IgG N-glycans promote adaptive immune responses through antibody-dependent cellular cytotoxicity (ADCC) and complement activation to combat infection or cancer and promote autoimmunity. In addition to the functional assays, researchers are examining the ability of protein-specific glycosylation to serve as biomarkers of disease. This literature review demonstrates that IgG N-glycans can discriminate between healthy controls, autoimmune disease, infectious disease, and cancer with high sensitivity. The literature also indicates that the IgG glycosylation patterns vary across disease state, thereby supporting their role as specific biomarkers. In addition, IgG N-glycans can be collected longitudinally from patients to track treatment responses or predict disease reoccurrence. This review focuses on IgG N-glycan profiles applied as diagnostics, cohort discriminators, and prognostics. Recent successes, remaining challenges, and upcoming approaches are critically discussed.

Filarial infections compromise influenza vaccination efficacy: Lessons from the mouse

Helminth parasites infect more than a quarter of the human population and inflict significant changes to the immunological status of their hosts. Several human studies report impaired responses to vaccinations in helminth-infected individuals. Analysing the impact of helminth infections on the efficacy of influenza vaccinations in the mouse system helps to elucidate the underlying immunological processes. Concurrent infection with the parasitic nematode Litomosoides sigmodontis reduced the quantity and quality of antibody responses to vaccination against seasonal influenza in BALB/c and C57BL/6 mice. This led to impaired vaccination-induced protection against challenge infections with the human pathogenic 2009 pandemic H1N1 influenza A virus in helminth-infected mice. Impaired responses were also observed if vaccinations were performed after immune-driven or drug-induced clearance of a previous helminth infection. Mechanistically, the suppression was associated with a systemic and sustained expansion of IL-10-producing CD4⁺CD49b⁺LAG-3⁺ type 1 regulatory T cells and partially abrogated by in vivo blockade of the IL-10 receptor. In summary, these findings raise the concern that individuals in helminth-endemic areas may not always benefit from vaccinations, even in the absence of an acute and diagnosable helminth infection.

Primary prevention of acute cardiovascular events by influenza vaccination: an observational study

AIMS

Previous studies show a reduced incidence of first myocardial infarction and stroke 1-3 months after influenza vaccination, but it is unclear how underlying cardiovascular risk impacts the association.

METHODS AND RESULTS

The study used linked Clinical Practice Research Datalink, Hospital Episode Statistics Admitted Patient Care and Office for National Statistics mortality data from England between 1 September 2008 and 31 August 2019. From the data, individuals aged 40-84 years with a first acute cardiovascular event and influenza vaccination occurring within 12 months of each September were selected. Using a self-controlled case series analysis, season-adjusted cardiovascular risk stratified incidence ratios (IRs) for cardiovascular events after vaccination compared with baseline time before and >120 days after vaccination were generated. 193 900 individuals with a first acute cardiovascular event and influenza vaccine were included. 105 539 had hypertension and 172 050 had a QRISK2 score ≥10%. In main analysis, acute cardiovascular event risk was reduced in the 15-28 days after vaccination [IR 0.72 (95% CI 0.70-0.74)] and, while the effect size tapered, remained reduced to 91-120 days after vaccination [0.83 (0.81-0.88)]. Reduced cardiovascular events were seen after vaccination among individuals of all age groups and with raised and low cardiovascular risk.

CONCLUSIONS

Influenza vaccine may offer cardiovascular benefit among individuals at varying cardiovascular risk. Further studies are needed to characterize the populations who could derive the most cardiovascular benefits from vaccination.

An Economic Comparison in the Elderly of Adjuvanted Quadrivalent Influenza Vaccine with Recombinant Quadrivalent Influenza Vaccine in Spain

Influenza infections impose a high burden of morbidity and mortality among older adults, at great cost to individuals and society. Enhanced influenza vaccines, which contain either an immune adjuvant or higher than normal doses of influenza virus antigens, are recommended for older adults. We used a health economics model to evaluate the cost effectiveness in Spain of a recently licensed recombinant quadrivalent influenza vaccine (QIVr), which contains three times the standard dose of influenza virus hemagglutinin but no neuraminidase, compared with an MF59-adjuvanted quadrivalent influenza vaccine (aQIV). Based on current tender prices in Spain and a conservative assumption that QIVr is 10.7% relatively more effective than aQIV, the incremental cost-effectiveness ratio (ICER) for QIVr was EUR 101,612.41 per quality-adjusted life year (QALY) gained. To meet the Spanish willingness-to-pay threshold of EUR 25,000 per QALY gained, QIVr would need to be 34.1% relatively more effective than aQIV. In a probabilistic sensitivity analysis conducted to confirm the robustness of the analysis, 99.7% of simulations for QIVr were higher than the willingness-to-pay curve. These findings suggest that QIVr is not currently a cost-effective influenza vaccine option relative to aQIV for older persons living in Spain.

Excess hospitalizations and mortality associated with seasonal influenza in Spain, 2008-2018

BACKGROUND

Influenza may trigger complications, particularly in at-risk groups, potentially leading to hospitalization or death. However, due to lack of routine testing, influenza cases are infrequently coded with influenza-specific diagnosis. Statistical models using influenza activity as an explanatory variable can be used to estimate annual hospitalizations and deaths associated with influenza. Our study aimed to estimate the clinical and economic burden of severe influenza in Spain, considering such models.

METHODS

The study comprised ten epidemic seasons (2008/2009-2017/2018) and used two approaches: (i) a direct method of estimating the seasonal influenza hospitalization, based on the number of National Health Service hospitalizations with influenza-specific International Classification of Diseases (ICD) codes (ICD-9: 487-488; ICD-10: J09-J11), as primary or secondary diagnosis; (ii) an indirect method of estimating excess hospitalizations and deaths using broader groups of ICD codes in time-series models, computed for six age groups and four groups of diagnoses: pneumonia or influenza (ICD-9: 480-488, 517.1; ICD-10: J09-J18), respiratory (ICD-9: 460-519; ICD-10: J00-J99), respiratory or cardiovascular (C&R, ICD-9: 390-459, 460-519; ICD-10: I00-I99, J00-J99), and all-cause. Means, excluding the H1N1pdm09 pandemic (2009/2010), are reported in this study.

RESULTS

The mean number of hospitalizations with a diagnosis of influenza per season was 13,063, corresponding to 28.1 cases per 100,000 people. The mean direct annual cost of these hospitalizations was €45.7 million, of which 65.7% was generated by patients with comorbidities. Mean annual influenza-associated C&R hospitalizations were estimated at 34,894 (min: 16,546; max: 52,861), corresponding to 75.0 cases per 100,000 (95% confidence interval [CI]: 63.3-86.3) for all ages and 335.3 (95% CI: 293.2-377.5) in patients aged ≥ 65 years. We estimate 3.8 influenza-associated excess C&R hospitalizations for each hospitalization coded with an influenza-specific diagnosis in patients aged ≥ 65 years. The mean direct annual cost of the estimated excess C&R hospitalizations was €142.9 million for all ages and €115.9 million for patients aged ≥ 65 years. Mean annual influenza-associated all-cause mortality per 100,000 people was estimated at 27.7 for all ages.

CONCLUSIONS

Results suggest a relevant under-detected burden of influenza mostly in the elderly population, but not neglectable in younger people.

Interactomics: Dozens of Viruses, Co-evolving With Humans, Including the Influenza A Virus, may Actively Distort Human Aging

Some viruses (e.g., human immunodeficiency virus 1 and severe acute respiratory syndrome coronavirus 2) have been experimentally proposed to accelerate features of human aging and of cellular senescence. These observations, along with evolutionary considerations on viral fitness, raised the more general puzzling hypothesis that, beyond documented sources in human genetics, aging in our species may also depend on virally encoded interactions distorting our aging to the benefits of diverse viruses. Accordingly, we designed systematic network-based analyses of the human and viral protein interactomes, which unraveled dozens of viruses encoding proteins experimentally demonstrated to interact with proteins from pathways associated with human aging, including cellular senescence. We further corroborated our predictions that specific viruses interfere with human aging using published experimental evidence and transcriptomic data; identifying influenza A virus (subtype H1N1) as a major candidate age distorter, notably through manipulation of cellular senescence. By providing original evidence that viruses may convergently contribute to the evolution of numerous age-associated pathways through co-evolution, our network-based and bipartite network-based methodologies support an ecosystemic study of aging, also searching for genetic causes of aging outside a focal aging species. Our findings, predicting age distorters and targets for anti-aging therapies among human viruses, could have fundamental and practical implications for evolutionary biology, aging study, virology, medicine, and demography.

Prevalence and Predictors of Seasonal Influenza Vaccine Uptake in Saudi Arabia Post COVID-19: A Web-Based Online Cross-Sectional Study

In the fall of 2022, the number of influenza-like illnesses (ILIs) and severe acute respiratory infections (SARIs) in Saudi Arabia had significantly increased compared with the corresponding period in previous years. Concerns regarding the population's seasonal influenza vaccine (SIV) uptake rates have emerged. In particular, the SIV uptake rates may have dropped post the COVID-19 pandemic compared with rates prior to the COVID-19 era. In this study, we aimed to estimate the prevalence and predictors of SIV uptake in Saudi Arabia post the COVID-19 pandemic. We conducted a cross-sectional study utilizing an online survey platform. We mainly collected sociodemographic information and determined whether the respondent was a healthcare professional or had a chronic disease. The overall SIV uptake prevalence was 31.8%. A lower SIV uptake was observed among those aged 55 years or older, females, residents of the central region, non-health practitioners, and those without chronic diseases. Several factors were associated with SIV uptake. Those aged 35-44 were over three-fold more likely to receive an SIV than those aged 55 years or older (OR: 3.66; 95% CI: 1.33-10.05). In addition, males had 73% higher odds of SIV uptake than females (OR: 1.73; 95% CI: 1.18-2.55). Health practitioners were more likely to receive an SIV than non-health practitioners (OR: 2.11; 95% CI: 1.45-3.06). Similarly, those with chronic diseases had 86% higher odds of SIV uptake than those without chronic diseases (OR: 1.86; 95% CI: 1.18-2.95). These findings can provide insights into the low prevalence and predictors of SIV uptake in Saudi Arabia. Future studies should be conducted to further explore the potential factors associated with such a low prevalence of SIV uptake post COVID-19 in Saudi Arabia.

The health of influenza surveillance and pandemic preparedness in the wake of the COVID-19 pandemic

The COVID-19 pandemic is the first to have emerged when Next Generation Sequencing was readily available and it has played the major role in following evolution of the causative agent, Severe Acute Respiratory Syndrome Coronavirus 2. Response to the pandemic was greatly facilitated though use of existing influenza surveillance networks: World Health Organization (WHO) Global Influenza Surveillance and Response System (GISRS), focussing largely on human influenza, and the OFFLU network of expertise on avian influenza established by the Food and Agricultural Organization of the United Nations (FAO) and the World Organization for Animal Health (WOAH). Data collection/deposition platforms associated with these networks, notably WHO's FluNet and the Global Initiative on Sharing All Influenza Data (GISAID) were/are being used intensely. Measures introduced to combat COVID-19 resulted in greatly decreased circulation of human seasonal influenza viruses for approximately 2 years, but circulation continued in the animal sector with an upsurge in the spread of highly pathogenic avian influenza subtype H5N1 with large numbers of wild bird deaths, culling of many poultry flocks and sporadic spill over into mammalian species, including humans, thereby increasing pandemic risk potential. While there are proposals/implementations to extend use of GISRS and GISAID to other infectious disease agents (e.g. Respiratory Syncytial Virus and Monkeypox), there is need to ensure that influenza surveillance is maintained and improved in both human and animal sectors in a sustainable manner to be truly prepared (early detection) for the next influenza pandemic.

Predictors of Seasonal Influenza Vaccination Willingness among High-Risk Populations Three Years after the Onset of the COVID-19 Pandemic

High-risk populations are at increased risk of severe influenza-related illness, hospitalization, and death due to influenza. The aim of our study was to assess the willingness of high-risk populations to take the influenza vaccine for the 2022-2023 season, and to investigate the factors associated with such willingness. We conducted a cross-sectional study in Greece in September 2022 using a convenience sample. We considered demographic characteristics, COVID-19-related variables, resilience, social support, anxiety, depression, and COVID-19-related burnout as potential predictors. Among participants, 39.4% were willing to accept the seasonal influenza vaccine, 33.9% were unwilling, and 26.8% were hesitant. Multivariable analysis identified that increased age and increased family support were associated with increased influenza vaccination willingness. Moreover, participants that have received COVID-19 booster doses were more willing to accept the influenza vaccine. In contrast, adverse effects because of COVID-19 vaccination and exhaustion due to measures against COVID-19 reduced influenza vaccination willingness. We found that the intention of high-risk populations to receive the influenza vaccine was low. Our study contributes to an increased understanding of the factors that affect vaccination willingness. Public health authorities could use this information to update vaccination programs against influenza. Emphasis should be given on safety and effectiveness issues.

mRNA vaccines: The future of prevention of viral infections?

Messenger RNA (mRNA) vaccines against COVID-19 are the first authorized biological preparations developed using this platform. During the pandemic, their administration has been proven to be a life-saving intervention. Here, we review the main advantages of using mRNA vaccines, identify further technological challenges to be met during the development of the mRNA platform, and provide an update on the clinical progress on leading mRNA vaccine candidates against different viruses that include influenza viruses, human immunodeficiency virus 1, respiratory syncytial virus, Nipah virus, Zika virus, human cytomegalovirus, and Epstein-Barr virus. The prospects and challenges of manufacturing mRNA vaccines in low-income countries are also discussed. The ongoing interest and research in mRNA technology are likely to overcome some existing challenges for this technology (e.g., related to storage conditions and immunogenicity of some components of lipid nanoparticles) and enhance the portfolio of vaccines against diseases for which classical formulations are already authorized. It may also open novel pathways of protection against infections and their consequences for which no safe and efficient immunization methods are currently available.

Association of post-vaccination adverse reactions after influenza vaccine with mortality and cardiopulmonary outcomes in patients with high-risk cardiovascular disease: the INVESTED trial

AIMS

Influenza vaccination is associated with reduced cardiopulmonary morbidity and mortality among patients with heart failure or recent myocardial infarction. The immune response to vaccination frequently results in mild adverse reactions (AR), which leads to vaccine hesitancy. This post hoc analysis explored the association between vaccine-related AR and morbidity and mortality in patients with high-risk cardiovascular disease.

METHODS AND RESULTS

The INVESTED trial randomized 5260 patients with recent heart failure hospitalization or acute myocardial infarction to high-dose trivalent or standard-dose quadrivalent inactivated influenza vaccine. We examined the association between vaccine-related AR and adverse clinical outcomes across both treatment groups in propensity-adjusted models. Among 5210 participants with available information on post-vaccination symptoms, 1968 participants (37.8%) experienced a vaccine-related AR. Compared to those without AR, post-vaccination AR, most commonly injection site pain (60.3%), were associated with lower risk for the composite of all-cause death or cardiopulmonary hospitalization (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.75-0.92, p < 0.001), cardiopulmonary hospitalizations (HR 0.85 [95% CI 0.76-0.95], p = 0.003), all-cause death (HR 0.77 [95% CI 0.62-0.96], p = 0.02), cardiovascular hospitalizations (HR 0.88 [95% CI 0.78-0.99], p = 0.03) and non-cardiopulmonary hospitalizations (HR 0.80 [95% CI 0.69-0.92], p = 0.003). While mild (76.4%) and moderate (20.6%) AR were most common and together associated with lower risk for the primary outcome (HR 0.81 [95% CI 0.74-0.90], p < 0.001), severe AR (2.9%) were related to increased risk (HR 1.68 [95% CI 1.17-2.42], p = 0.005).

CONCLUSION

Mild to moderate post-vaccination reactions after influenza vaccine were associated with reduced risk of cardiopulmonary hospitalizations and all-cause mortality in patients with high-risk cardiovascular disease, while severe reactions may indicate increased risk. Mild to moderate AR to influenza vaccination may be a marker of immune response and should not deter future vaccinations.

The Impact of Cold Ambient Temperature in the Pattern of Influenza Virus Infection

Background

Prior literature suggests that cold temperature strongly influences the immune function of animals and human behaviors, which may allow for the transmission of respiratory viral infections. However, information on the impact of cold stimuli, especially the impact of temporal change in the ambient temperature on influenza virus transmission, is limited.

Methods

A susceptible-infected-recovered-susceptible model was applied to evaluate the effect of temperature change on influenza virus transmission.

Results

The mean temperature of the prior week was positively associated with the number of newly diagnosed cases (0.107 [95% Bayesian credible interval {BCI}, .106-.109]), whereas the mean difference in the temperature of the prior week was negatively associated (-0.835 [95% BCI, -.840 to -.830]). The product of the mean temperature and mean difference in the temperature of the previous week were also negatively associated with the number of newly diagnosed cases (-0.192 [95% BCI, -.197 to -.187]).

Conclusions

The mean temperature and the mean difference in temperature affected the number of newly diagnosed influenza cases differently. Our data suggest that high ambient temperature and a drop in the temperature and their interaction increase the risk of infection. Therefore, the highest risk of infection is attributable to a steep fall in temperature in a relatively warm environment.

Global and national influenza-associated hospitalisation rates: Estimates for 40 countries and administrative regions

Background

WHO estimates that seasonal influenza epidemics result in three to five million cases of severe illness (hospitalisations) every year. We aimed to improve the understanding of influenza-associated hospitalisation estimates at a national and global level.

Methods

We performed a systematic literature review of English- and Chinese-language studies published between 1995 and 2020 estimating influenza-associated hospitalisation. We included a total of 127 studies (seven in Chinese) in the meta-analysis and analyzed their data using a logit-logistic regression model to understand the influence of five study factors and produce national and global estimates by age groups. The five study factors assessed were: 1) the method used to calculate the influenza-associated hospitalisation estimates (rate- or time series regression-based), 2) the outcome measure (divided into three envelopes: narrow, medium, or wide), 3) whether every case was laboratory-confirmed or not, 4) whether the estimates were national or sub-national, 5) whether the rates were based on a single year or multiple years.

Results

The overall pooled influenza-associated hospitalisation rate was 40.5 (95% confidence interval (CI) = 24.3-67.4) per 100 000 persons, with rates varying substantially by age: 224.0 (95% CI = 118.8-420.0) in children aged 0-4 years and 96.8 (95% CI = 57.0-164.3) in the elderly aged >65 years. The overall pooled hospitalisation rates varied by calculation method; for all ages, the rates were significantly higher when they were based on rate-based methods or calculated on a single season and significantly lower when cases were laboratory-confirmed. The national hospitalisation rates (all ages) varied considerably, ranging from 11.7 (95% CI = 3.8-36.3) per 100 000 in New Zealand to 122.1 (95% CI = 41.5-358.4) per 100 000 in India (all age estimates).

Conclusions

Using the pooled global influenza-associated hospitalisation rate, we estimate that seasonal influenza epidemics result in 3.2 million cases of severe illness (hospitalisations) per annum. More extensive analyses are required to assess the influence of other factors on the estimates (e.g. vaccination and dominant virus (sub)types) and efforts to harmonize the methods should be encouraged. Our study highlights the high rates of influenza-associated hospitalisations in children aged 0-4 years and the elderly aged 65+ years.

Comparative Surface Electrostatics and Normal Mode Analysis of High and Low Pathogenic H7N7 Avian Influenza Viruses

Influenza A viruses are rarely symptomatic in wild birds, while representing a higher threat to poultry and mammals, where they can cause a variety of symptoms, including death. H5 and H7 subtypes of influenza viruses are of particular interest because of their pathogenic potential and reported capacity to spread from poultry to mammals, including humans. The identification of molecular fingerprints for pathogenicity can help surveillance and early warning systems, which are crucial to prevention and protection from such potentially pandemic agents. In the past decade, comparative analysis of the surface features of hemagglutinin, the main protein antigen in influenza viruses, identified electrostatic fingerprints in the evolution and spreading of H5 and H9 subtypes. Electrostatic variation among viruses from avian or mammalian hosts was also associated with host jump. Recent findings of fingerprints associated with low and highly pathogenic H5N1 viruses, obtained by means of comparative electrostatics and normal modes analysis, prompted us to check whether such fingerprints can also be found in the H7 subtype. Indeed, evidence presented in this work showed that also in H7N7, hemagglutinin proteins from low and highly pathogenic strains present differences in surface electrostatics, while no meaningful variation was found in normal modes.

COVID-19 mortality attenuated during widespread Omicron transmission, Denmark, 2020 to 2022

BackgroundIt sparked considerable attention from international media when Denmark lifted restrictions against COVID-19 in February 2022 amidst widespread transmission of the new SARS-CoV-2 Omicron variant and a steep rise in reported COVID-19 mortality based on the 30-day COVID-19 death count.AimOur aim was to investigate how coincidental infections affected COVID-19 mortality estimates following the introduction of the Omicron variant in late 2021.MethodsWe compared the 30-day COVID-19 death count with the observed mortality using three alternative mortality estimation methods; (i) a mathematical model to correct the 30-day COVID-19 death count for coincidental deaths, (ii) the Causes of Death Registry (CDR) and (iii) all-cause excess mortality.ResultsThere was a substantial peak in the 30-day COVID-19 death count following the emergence of the Omicron variant in late 2021. However, there was also a substantial change in the proportion of coincidental deaths, increasing from 10-20% to around 40% of the recorded COVID-19 deaths. The high number of 30-day COVID-19 deaths was not reflected in the number of COVID-19 deaths in the CDR and the all-cause excess mortality surveillance.ConclusionOur analysis showed a distinct change in the mortality pattern following the introduction of Omicron in late 2021 with a markedly higher proportion of people estimated to have died with, rather than of, COVID-19 compared with mortality patterns observed earlier in the COVID-19 pandemic. Our findings highlight the importance of incorporating alternative mortality surveillance methods to more correctly estimate the burden of COVID-19 as the pandemic continues to evolve.

Urine Metabolome Dynamics Discriminate Influenza Vaccination Response

Influenza represents a major and ongoing public health hazard. Current collaborative efforts are aimed toward creating a universal flu vaccine with the goals of both improving responses to vaccination and increasing the breadth of protection against multiple strains and clades from a single vaccine. As an intermediate step toward these goals, the current work is focused on evaluating the systemic host response to vaccination in both normal and high-risk populations, such as the obese and geriatric populations, which have been linked to poor responses to vaccination. We therefore employed a metabolomics approach using a time-course (n = 5 time points) of the response to human vaccination against influenza from the time before vaccination (pre) to 90 days following vaccination. We analyzed the urinary profiles of a cohort of subjects (n = 179) designed to evenly sample across age, sex, BMI, and other demographic factors, stratifying their responses to vaccination as “High”, “Low”, or “None” based on the seroconversion measured by hemagglutination inhibition assay (HAI) from plasma samples at day 28 post-vaccination. Overall, we putatively identified 15,903 distinct, named, small-molecule structures (4473 at 10% FDR) among the 895 samples analyzed, with the aim of identifying metabolite correlates of the vaccine response, as well as prognostic and diagnostic markers from the periods before and after vaccination, respectively. Notably, we found that the metabolic profiles could unbiasedly separate the high-risk High-responders from the high-risk None-responders (obese/geriatric) within 3 days post-vaccination. The purine metabolites Guanine and Hypoxanthine were negatively associated with high seroconversion (p = 0.0032, p < 0.0001, respectively), while Acetyl-Leucine and 5-Aminovaleric acid were positively associated. Further changes in Cystine, Glutamic acid, Kynurenine and other metabolites implicated early oxidative stress (3 days) after vaccination as a hallmark of the High-responders. Ongoing efforts are aimed toward validating these putative markers using a ferret model of influenza infection, as well as an independent cohort of human seasonal vaccination and human challenge studies with live virus.

Clinical Features of COVID-19, Dengue, and Influenza among Adults Presenting to Emergency Departments and Urgent Care Clinics-Puerto Rico, 2012-2021

Dengue and influenza are pathogens of global concern and cause febrile illness similar to COVID-19. We analyzed data from an enhanced surveillance system operating from three emergency departments and an urgent care clinic in Puerto Rico to identify clinical features predictive of influenza or dengue compared with COVID-19. Participants with fever or respiratory symptoms and aged ≥18 years enrolled May 2012-January 2021 with dengue, influenza, or SARS-CoV-2 confirmed by reverse transcriptase polymerase chain reaction were included. We calculated adjusted odds ratios (aORs) and 95% CIs using logistic regression to assess clinical characteristics of participants with COVID-19 compared to those with dengue or influenza, adjusting for age, subregion, and days from illness onset to presentation for clinical care. Among 13,431 participants, we identified 2,643 with dengue (N = 303), influenza (N = 2,064), or COVID-19 (N = 276). We found differences in days from onset to presentation among influenza (2 days [interquartile range: 1-3]), dengue (3 days [2-4]), and COVID-19 cases (4 days [2-7]; P < 0.001). Cough (aOR: 0.12 [95% CI: 0.07-0.19]) and shortness of breath (0.18 [0.08-0.44]) were less common in dengue compared with COVID-19. Facial flushing (20.6 [9.8-43.5]) and thrombocytopenia (24.4 [13.3-45.0]) were more common in dengue. Runny nose was more common in influenza compared with COVID-19 (8.3 [5.8-12.1]). In summary, cough, shortness of breath, facial flushing, and thrombocytopenia helped distinguish between dengue and COVID-19. Although few features distinguished influenza from COVID-19, presentation > 4 days after symptom onset suggests COVID-19. These findings may assist clinicians making time-sensitive decisions regarding triage, isolation, and management while awaiting pathogen-specific testing.

Expiratory Aerosol pH: The Overlooked Driver of Airborne Virus Inactivation

Respiratory viruses, including influenza virus and SARS-CoV-2, are transmitted by the airborne route. Air filtration and ventilation mechanically reduce the concentration of airborne viruses and are necessary tools for disease mitigation. However, they ignore the potential impact of the chemical environment surrounding aerosolized viruses, which determines the aerosol pH. Atmospheric aerosol gravitates toward acidic pH, and enveloped viruses are prone to inactivation at strong acidity levels. Yet, the acidity of expiratory aerosol particles and its effect on airborne virus persistence have not been examined. Here, we combine pH-dependent inactivation rates of influenza A virus (IAV) and SARS-CoV-2 with microphysical properties of respiratory fluids using a biophysical aerosol model. We find that particles exhaled into indoor air (with relative humidity ≥ 50%) become mildly acidic (pH ∼ 4), rapidly inactivating IAV within minutes, whereas SARS-CoV-2 requires days. If indoor air is enriched with nonhazardous levels of nitric acid, aerosol pH drops by up to 2 units, decreasing 99%-inactivation times for both viruses in small aerosol particles to below 30 s. Conversely, unintentional removal of volatile acids from indoor air may elevate pH and prolong airborne virus persistence. The overlooked role of aerosol acidity has profound implications for virus transmission and mitigation strategies.

Associations of influenza and pneumococcal vaccinations with burdens of older family caregivers: The Japan Gerontological Evaluation study (JAGES) cross-sectional study

BACKGROUND

Influenza and pneumonia tend to be severe in older adults; thus, vaccination is necessary to prevent these illnesses. Vaccination is especially important for older family caregivers (OFCs) not only to prevent them from becoming ill, but also to prevent secondary infections in the family care receivers (FCRs), who are mostly frail older adults and have a higher risk of severe illness. Thus, we investigated whether caregiving burdens were associated with the vaccinations among older adults.

METHODS

We used cross-sectional data from the Japan Gerontological Evaluation Study (JAGES), which was conducted in 64 Japanese municipalities from November 2019 to January 2020. The target population consisted of 26,177 individuals aged 65 years or older who were independent and did not need public long-term care. The primary outcome was the uptakes of either or both influenza and pneumococcal vaccinations. Multinomial logistic regressions were performed, setting those who underwent neither vaccinations as the reference group.

RESULTS

Among the participants, 23.3 %, 25.8 %, 9.4 %, or 41.5 % underwent neither, only influenza, only pneumococcal, or the both vaccinations, respectively. The caregiving frequency, time length in a day, or dementia of FCR were negatively associated with influenza vaccination (caregiving almost every day: relative risk ratio {RRR}: 0.39, 95 % confident interval {95 % CI} [0.24-0.63]; caregiving almost all day: 0.44, 95 % CI: 0.23-0.85; caregiving for FCR: RRR:0.55, 95 % CI: 0.34-0.91). On the other hand, those caregiving burdens were not associated with pneumococcal only or the both vaccinations. Having a family physician mitigated all the negative effect of the caregiving burdens on the vaccinations.

CONCLUSION

Our results suggest that the caregiving burden is a barrier to influenza vaccination but not to pneumococcal vaccination and that having a physician mitigates the negative effect regardless of the burden kind.

Mitigating co-circulation of seasonal influenza and COVID-19 pandemic in the presence of vaccination: A mathematical modeling approach

The co-circulation of two respiratory infections with similar symptoms in a population can significantly overburden a healthcare system by slowing the testing and treatment. The persistent emergence of contagious variants of SARS-CoV-2, along with imperfect vaccines and their waning protections, have increased the likelihood of new COVID-19 outbreaks taking place during a typical flu season. Here, we developed a mathematical model for the co-circulation dynamics of COVID-19 and influenza, under different scenarios of influenza vaccine coverage, COVID-19 vaccine booster coverage and efficacy, and testing capacity. We investigated the required minimal and optimal coverage of COVID-19 booster (third) and fourth doses, in conjunction with the influenza vaccine, to avoid the coincidence of infection peaks for both diseases in a single season. We show that the testing delay brought on by the high number of influenza cases impacts the dynamics of influenza and COVID-19 transmission. The earlier the peak of the flu season and the greater the number of infections with flu-like symptoms, the greater the risk of flu transmission, which slows down COVID-19 testing, resulting in the delay of complete isolation of patients with COVID-19 who have not been isolated before the clinical presentation of symptoms and have been continuing their normal daily activities. Furthermore, our simulations stress the importance of vaccine uptake for preventing infection, severe illness, and hospitalization at the individual level and for disease outbreak control at the population level to avoid putting strain on already weak and overwhelmed healthcare systems. As such, ensuring optimal vaccine coverage for COVID-19 and influenza to reduce the burden of these infections is paramount. We showed that by keeping the influenza vaccine coverage about 35% and increasing the coverage of booster or fourth dose of COVID-19 not only reduces the infections with COVID-19 but also can delay its peak time. If the influenza vaccine coverage is increased to 55%, unexpectedly, it increases the peak size of influenza infections slightly, while it reduces the peak size of COVID-19 as well as significantly delays the peaks of both of these diseases. Mask-wearing coupled with a moderate increase in the vaccine uptake may mitigate COVID-19 and prevent an influenza outbreak.

LAG-3 Contribution to T Cell Downmodulation during Acute Respiratory Viral Infections

LAG-3 is a type I transmembrane protein expressed on immune cells, such as activated T cells, and binds to MHC class II with high affinity. LAG-3 is an inhibitory receptor, and its multiple biological activities on T cell activation and effector functions play a regulatory role in the immune response. Immunotherapies directed at immune checkpoints, including LAG-3, have become a promising strategy for controlling malignant tumors and chronic viral diseases. Several studies have suggested an association between the expression of LAG-3 with an inadequate immune response during respiratory viral infections and the susceptibility to reinfections, which might be a consequence of the inhibition of T cell effector functions. However, important information relative to therapeutic potential during acute viral lower respiratory tract infections and the mechanism of action of the LAG-3 checkpoint remains to be characterized. In this article, we discuss the contribution of LAG-3 to the impairment of T cells during viral respiratory infections. Understanding the host immune response to respiratory infections is crucial for developing effective vaccines and therapies.

Impact of COVID-19 pandemic on influenza virus prevalence in children in Sichuan, China

We performed a retrospective analysis of influenza A and B virus antigen detection data in children in Sichuan Province from January 2019 to December 2021, with the goal of studying the impact of the COVID-19 pandemic on influenza circulation in children in Sichuan, China. During the pandemic, both the number of specimens and the positive rates of the influenza virus fell dramatically. The positivity for influenza A virus decreased from 22.5% in 2019 to 9.9% in 2020 to 0.2% in 2021 (p < 0.001). The lowest and highest positive rates for the influenza B virus occurred in 2020 and 2021, respectively, with a statistically significant 3-year comparison (p < 0.001). During the pandemic, the annual positivity remained higher in school-age than in preschoolers, while there was no difference in the annual positivity between the two gender groups, both consistent with the prepandemic results. During the pandemic, the seasonality of influenza A and B was different from that before the pandemic. In 2019, the epidemic season for influenza A was autumn and winter, while the epidemic season for influenza B was winter and spring. Seasonal changes in influenza A were insignificant after the pandemic, and influenza B became predominant in 2021, with a high prevalence in the autumn. Although influenza activity decreased during the COVID-19 pandemic, one should be on the lookout for a possible rebound in influenza circulation in the future.

Severe influenza infection is associated with inflammatory programmed cell death in infected macrophages

Introduction

Influenza A virus (IAV) is one of the leading causes of respiratory tract infections in humans, representing a major public health concern. The various types of cell death have a crucial role in IAV pathogenesis because this virus may trigger both apoptosis and necroptosis in airway epithelial cells in parallel. Macrophages play an important role in the clearance of virus particles, priming the adaptive immune response in influenza. However, the contribution of macrophage death to pathogenesis of IAV infection remains unclear.

Methods

In this work, we investigated IAV-induced macrophage death, along with potential therapeutic intervention. We conducted in vitro and in vivo experiments to evaluate the mechanism and the contribution of macrophages death to the inflammatory response induced by IAV infection.

Results

We found that IAV or its surface glycoprotein hemagglutinin (HA) triggers inflammatory programmed cell death in human and murine macrophages in a Toll-like receptor-4 (TLR4)- and TNF-dependent manner. Anti-TNF treatment in vivo with the clinically approved drug etanercept prevented the engagement of the necroptotic loop and mouse mortality. Etanercept impaired the IAV-induced proinflammatory cytokine storm and lung injury.

Conclusion

In summary, we demonstrated a positive feedback loop of events that led to necroptosis and exacerbated inflammation in IAV-infected macrophages. Our results highlight an additional mechanism involved in severe influenza that could be attenuated with clinically available therapies.

Short-term effects of ambient particulate matter (PM1, PM2.5 and PM10) on influenza-like illness in Guangzhou, China

BACKGROUND

Particulate matter (PM) has been linked to respiratory infections in a growing body of evidence. Studies on the relationship between ILI (influenza-like illness) and PM₁ (particulate matter with aerodynamic diameter ≤1 μm) are, however, scarce. The purpose of this study was to investigate the effects of PM on ILI in Guangzhou, China.

METHODS

Daily ILI cases, air pollution records (PM₁, PM_2.5, PM₁₀ and gaseous pollutants), and metrological data between 2014 and 2019 were gathered from Guangzhou, China. To estimate the risk of ILI linked with exposure to PM pollutants, a quasi-Poisson regression was used. Additionally, subgroup analyses stratified by gender, age and season were carried out.

RESULTS

For each 10 μg/m³ increase of PM₁ and PM_2.5 over the past two days (lag01), and PM₁₀ over the past three days (lag02), the relative risks (RR) of ILI were 1.079 (95% confidence interval [CI]: 1.050, 1.109), 1.044 (95% CI: 1.027, 1.062) and 1.046 (95% CI: 1.032, 1.059), respectively. The estimated risks for men and women were substantially similar. The effects of PM pollutants between male and female were basically equivalent. People aged 15-24 years old were more susceptive to PM pollutants.

CONCLUSIONS

It implies that PM₁, PM_2.5 and PM₁₀ are all risk factors for ILI, the health impacts of PM pollutants vary by particle size. Reducing the concentration of PM₁ needs to be considered when generating a strategy to prevent ILI.

Alternative antiviral approaches to combat influenza A virus

Influenza A (IAV) is a major human respiratory pathogen that contributes to a significant threat to health security, worldwide. Despite vaccinations and previous immunisations through infections, humans can still be infected with influenza several times throughout their lives. This phenomenon is attributed to the antigenic changes of hemagglutinin (HA) and neuraminidase (NA) proteins in IAV via genetic mutation and reassortment, conferring antigenic drift and antigenic shift, respectively. Numerous findings indicate that slow antigenic drift and reassortment-derived antigenic shift exhibited by IAV are key processes that allow IAVs to overcome the previously acquired host immunity, which eventually leads to the annual re-emergence of seasonal influenza and even pandemic influenza, in rare occasions. As a result, current therapeutic options hit a brick wall quickly. As IAV remains a constant threat for new outbreaks worldwide, the underlying processes of genetic changes and alternative antiviral approaches for IAV should be further explored to improve disease management. In the light of the above, this review discusses the characteristics and mechanisms of mutations and reassortments that contribute to IAV's evolution. We also discuss several alternative RNA-targeting antiviral approaches, namely the CRISPR/Cas13 systems, RNA interference (RNAi), and antisense oligonucleotides (ASO) as potential antiviral approaches against IAV.

Impact of air pollutants on influenza-like illness outpatient visits under urbanization process in the sub-center of Beijing, China

Air pollutants can cause serious harm to human health and a variety of respiratory diseases. This study aimed to explore the associations between air pollutants and outpatient visits for influenza-like illness (ILI) under urbanization process in the sub-center of Beijing. The data of ILI in sub-center of Beijing from April 1, 2014 to December 31, 2020 were obtained from Beijing Influenza Surveillance Network. A generalized additive Poisson model was applied to examine the associations between the concentrations of air pollutants and daily outpatient visits for ILI when controlling meteorological factors and holidays. A total of 322,559 patients with ILI were included. The results showed that in the early urbanization period, the effects of PM_2.5, PM₁₀, SO₂, O₃, and CO on lag0 day, and PM_2.5, PM₁₀, O₃, and CO on lag1 day were not significant. In the later urbanization period, AQI and the concentrations of PM_2.5, PM₁₀, SO₂, NO₂ and CO on lag1 day were all significantly associated with an increased risk of outpatient visits for ILI, which increased by 0.34% (95%CI 0.23%, 0.45%), 0.42% (95%CI 0.29%, 0.56%), 0.44% (95%CI 0.33%, 0.55%), 0.36% (95%CI 0.24%, 0.49%), 0.91% (95%CI 0.62%, 1.21%) and 0.38% (95%CI 0.26%, 0.49%). The concentration of O₃ on lag1 day was significantly associated with a decreased risk of outpatient visits for ILI, which decreased by 0.21% (95%CI 0.04%, 0.39%). We found that the urbanization process had significantly aggravated the impact of air pollutants on ILI outpatient visits. These findings expand the current knowledge of ILI outpatient visits correlated with air pollutants under urbanization process.

The Structural Identifiability of a Humidity-Driven Epidemiological Model of Influenza Transmission

Influenza epidemics cause considerable morbidity and mortality every year worldwide. Climate-driven epidemiological models are mainstream tools to understand seasonal transmission dynamics and predict future trends of influenza activity, especially in temperate regions. Testing the structural identifiability of these models is a fundamental prerequisite for the model to be applied in practice, by assessing whether the unknown model parameters can be uniquely determined from epidemic data. In this study, we applied a scaling method to analyse the structural identifiability of four types of commonly used humidity-driven epidemiological models. Specifically, we investigated whether the key epidemiological parameters (i.e., infectious period, the average duration of immunity, the average latency period, and the maximum and minimum daily basic reproductive number) can be uniquely determined simultaneously when prevalence data is observable. We found that each model is identifiable when the prevalence of infection is observable. The structural identifiability of these models will lay the foundation for testing practical identifiability in the future using synthetic prevalence data when considering observation noise. In practice, epidemiological models should be examined with caution before using them to estimate model parameters from epidemic data.

A universal influenza mRNA vaccine candidate boosts T cell responses and reduces zoonotic influenza virus disease in ferrets

Universal influenza vaccines should protect against continuously evolving and newly emerging influenza viruses. T cells may be an essential target of such vaccines, as they can clear infected cells through recognition of conserved influenza virus epitopes. We evaluated a novel T cell-inducing nucleoside-modified messenger RNA (mRNA) vaccine that encodes the conserved nucleoprotein, matrix protein 1, and polymerase basic protein 1 of an H1N1 influenza virus. To mimic the human situation, we applied the mRNA vaccine as a prime-boost regimen in naïve ferrets (mimicking young children) and as a booster in influenza-experienced ferrets (mimicking adults). The vaccine induced and boosted broadly reactive T cells in the circulation, bone marrow, and respiratory tract. Booster vaccination enhanced protection against heterosubtypic infection with a potential pandemic H7N9 influenza virus in influenza-experienced ferrets. Our findings show that mRNA vaccines encoding internal influenza virus proteins represent a promising strategy to induce broadly protective T cell immunity against influenza viruses.

Study on the influence of meteorological factors on influenza in different regions and predictions based on an LSTM algorithm

BACKGROUND

Influenza epidemics pose a threat to human health. It has been reported that meteorological factors (MFs) are associated with influenza. This study aimed to explore the similarities and differences between the influences of more comprehensive MFs on influenza in cities with different economic, geographical and climatic characteristics in Fujian Province. Then, the information was used to predict the daily number of cases of influenza in various cities based on MFs to provide bases for early warning systems and outbreak prevention.

METHOD

Distributed lag nonlinear models (DLNMs) were used to analyse the influence of MFs on influenza in different regions of Fujian Province from 2010 to 2021. Long short-term memory (LSTM) was used to train and model daily cases of influenza in 2010-2018, 2010-2019, and 2010-2020 based on meteorological daily values. Daily cases of influenza in 2019, 2020 and 2021 were predicted. The root mean squared error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE) and symmetric mean absolute percentage error (SMAPE) were used to quantify the accuracy of model predictions.

RESULTS

The cumulative effect of low and high values of air pressure (PRS), air temperature (TEM), air temperature difference (TEMD) and sunshine duration (SSD) on the risk of influenza was obvious. Low (< 979 hPa), medium (983 to 987 hPa) and high (> 112 hPa) PRS were associated with a higher risk of influenza in women, children aged 0 to 12 years, and rural populations. Low (< 9 °C) and high (> 23 °C) TEM were risk factors for influenza in four cities. Wind speed (WIN) had a more significant effect on the risk of influenza in the ≥ 60-year-old group. Low (< 40%) and high (> 80%) relative humidity (RHU) in Fuzhou and Xiamen had a significant effect on influenza. When PRS was between 1005-1015 hPa, RHU > 60%, PRE was low, TEM was between 10-20 °C, and WIN was low, the interaction between different MFs and influenza was most obvious. The RMSE, MAE, MAPE, and SMAPE evaluation indices of the predictions in 2019, 2020 and 2021 were low, and the prediction accuracy was high.

CONCLUSION

All eight MFs studied had an impact on influenza in four cities, but there were similarities and differences. The LSTM model, combined with these eight MFs, was highly accurate in predicting the daily cases of influenza. These MFs and prediction models could be incorporated into the influenza early warning and prediction system of each city and used as a reference to formulate prevention strategies for relevant departments.

Depression, aging, and immunity: implications for COVID-19 vaccine immunogenicity

The aging process can have detrimental effects on the immune system rendering the elderly more susceptible to infectious disease and less responsive to vaccination. Major depressive disorder (MDD) has been hypothesized to show characteristics of accelerated biological aging. This raises the possibility that depressed individuals will show some overlap with elderly populations with respect to their immune response to infection and vaccination. Here we provide an umbrella review of this literature in the context of the SARS CoV-2 pandemic. On balance, the available data do indeed suggest that depression is a risk factor for both adverse outcomes following COVID-19 infection and for reduced COVID-19 vaccine immunogenicity. We conclude that MDD (and other major psychiatric disorders) should be recognized as vulnerable populations that receive priority for vaccination along with other at-risk groups.

Life Satisfaction and Influenza Vaccination Among Older Adults in Canada

Older adults have an increased risk of complications or death from influenza. Despite the benefits of vaccination for older adults, vaccination coverage among older adults ages 65 years and over is still below Canada's national target of 80 per cent. As health-care-seeking behaviours are influenced by several factors, including life satisfaction, we investigated the relationship between life satisfaction and influenza vaccination among older adults. A sample (n = 22,424) from the 2015-2016 Canadian Community Health Survey data was analysed using descriptive and multinomial logistic regression analyses. Higher life satisfaction was associated with a more recent influenza vaccination history. Vaccination differed by gender, age, and self-reported health status, as women, much older adults, and those with the poorest health status were more likely to be vaccinated. The study suggests an association between life satisfaction and influenza vaccination. More research into the factors that impact influenza vaccination in older adults is needed to increase vaccination coverage in the older adult population.

Public health and budget impacts of switching from a trivalent to a quadrivalent inactivated influenza vaccine in Paraguay

This study aimed to investigate the public health and economic benefit of using a quadrivalent influenza vaccine (QIV) instead of a trivalent influenza vaccine (TIV) in past seasons in Paraguay. The budget impact of switching from TIV to QIV in the Immunization Program was also evaluated. The adapted model includes two modules. The first compared retrospectively Health and Economic outcomes resulting from the use of QIV instead of TIV. The second forecast the spending and savings that would be associated with the switch from TIV to QIV. Our findings estimate that the switch from TIV to QIV during the seasons 2012 to 2017 could have prevented around 2,600 influenza cases, 67 hospitalizations and 10 deaths. An alternative scenario using standardized estimates of the burden of influenza showed that 234 influenza-related hospitalizations and 29 deaths could have been prevented. The estimated annual budget impact of a full switch from TIV to QIV was around USD1,6 million both from the payer and societal perspectives. Those results are mainly driven by vaccine prices and coverage rate. In sum, this manuscript describes how the use of QIV instead of TIV could have prevented influenza cases and subsequent complications that led to hospitalizations and deaths. This could have generated savings for the health system and society, offsetting part of the additional investment needed to switch from TIV to QIV.

Lianhuaqingwen capsule inhibits non-lethal doses of influenza virus-induced secondary Staphylococcus aureus infection in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Lianhuaqingwen capsule (LH-C) is a traditional Chinese medicine (TCM), consisting of two prescriptions, Ma-xing-shi-gan-tang (MXSGT) and Yinqiao San. It has been proven to have antiviral, antibacterial, and immunomodulatory effects in recent years. Clinically, it is commonly used in the treatment of respiratory tract infections.

AIM OF THE STUDY

It was demonstrated in our previous studies that LH-C has an effect of antivirus and inhibits influenza virus-induced bacterial adhesion to respiratory epithelial cells through down-regulation of cell adhesion molecules in vitro. However, LH-C's effect against influenza-induced secondary bacterial infection in animal studies remains unclear. Therefore, in the present study, we established a mouse model of infection with non-lethal doses of influenza virus(H1N1) and secondary infection of Staphylococcus aureus (S. aureus), to investigate the potential effects of LH-C.

METHODS

Experiments were carried out on BALB/c mice infecting non-lethal doses of H1N1 and non-lethal doses of S. aureus, and the viral, and bacterial doses were determined by observing and recording changes in the body weight, mortality, and pathological changes. Moreover, after LH-C treatment, the survival rate, body weight, lung index, viral titers, bacterial colonies, pathological changes, and the inflammatory cytokines in the mouse model have all been systematically determined.

RESULTS

In the superinfection models of H1N1 and S. aureus, the mortality rate was 100% in groups of mice infected with 20 PFU/50 μL of H1N1 and 10⁵ CFU/mL of S. aureus, 20 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus, 4 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus. The mortality rate was 50% in the group of mice infected with 4 PFU/50 μL of H1N1 and 10⁵ CFU/mL of S. aureus. The mortality rate was 37.5% in the group of mice infected with 20 PFU/50 μL of H1N1 alone and in the group of mice infected with 2 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus. The mortality rate in the group of mice infected with 2 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus was 30%. The infected mice of 2 PFU/50 μL of H1N1 and 10⁶ CFU/mL of S. aureus had a weight loss of nearly 10%. About the histopathological changes in the lung tissue of infection mice, severe lung lesions were found in the superinfection models. LH-C improved survival in the superinfected mice, significantly reduced lung index, lowered viral titers and bacterial loads, and alleviated lung damage. It reduced lung inflammation by down-regulating mRNA expression levels of inflammatory mediators like IL-6, IL-1β, IL-10, TNF-α, IFN-β, MCP-1, and RANTES.

CONCLUSIONS

We found that superinfection from non-lethal doses of S. aureus following non-lethal doses of H1N1 was equally fatal in mice, confirming the severity of secondary infections. The ability of LH-C to alleviate lung injury resulting from secondary S. aureus infection induced by H1N1 was confirmed. These findings provided a further assessment of LH-C, suggesting that LH-C may have good therapeutic efficacy in influenza secondary bacterial infection disease.

The memory B cell response to influenza vaccination is impaired in older persons

Influenza infection imparts an age-related increase in mortality and morbidity. The most effective countermeasure is vaccination; however, vaccines offer modest protection in older adults. To investigate how aging impacts the memory B cell response, we track hemagglutinin-specific B cells by indexed flow sorting and single-cell RNA sequencing (scRNA-seq) in 20 healthy adults that were administered the trivalent influenza vaccine. We demonstrate age-related skewing in the memory B cell compartment 6 weeks after vaccination, with younger adults developing hemagglutinin-specific memory B cells with an FcRL5+ "atypical" phenotype, showing evidence of somatic hypermutation and positive selection, which happened to a lesser extent in older persons. We use publicly available scRNA-seq from paired human lymph node and blood samples to corroborate that FcRL5+ atypical memory B cells can derive from germinal center (GC) precursors. Together, this study shows that the aged human GC reaction and memory B cell response following vaccination is defective.

Autoantibodies against type I IFNs in patients with critical influenza pneumonia

Autoantibodies neutralizing type I interferons (IFNs) can underlie critical COVID-19 pneumonia and yellow fever vaccine disease. We report here on 13 patients harboring autoantibodies neutralizing IFN-α2 alone (five patients) or with IFN-ω (eight patients) from a cohort of 279 patients (4.7%) aged 6-73 yr with critical influenza pneumonia. Nine and four patients had antibodies neutralizing high and low concentrations, respectively, of IFN-α2, and six and two patients had antibodies neutralizing high and low concentrations, respectively, of IFN-ω. The patients' autoantibodies increased influenza A virus replication in both A549 cells and reconstituted human airway epithelia. The prevalence of these antibodies was significantly higher than that in the general population for patients <70 yr of age (5.7 vs. 1.1%, P = 2.2 × 10-5), but not >70 yr of age (3.1 vs. 4.4%, P = 0.68). The risk of critical influenza was highest in patients with antibodies neutralizing high concentrations of both IFN-α2 and IFN-ω (OR = 11.7, P = 1.3 × 10-5), especially those <70 yr old (OR = 139.9, P = 3.1 × 10-10). We also identified 10 patients in additional influenza patient cohorts. Autoantibodies neutralizing type I IFNs account for ∼5% of cases of life-threatening influenza pneumonia in patients <70 yr old.

Cellular glycan modification by B3GAT1 broadly restricts influenza virus infection

Communicable respiratory viral infections pose both epidemic and pandemic threats and broad-spectrum antiviral strategies could improve preparedness for these events. To discover host antiviral restriction factors that may act as suitable targets for the development of host-directed antiviral therapies, we here conduct a whole-genome CRISPR activation screen with influenza B virus (IBV). A top hit from our screen, beta-1,3-glucuronyltransferase 1 (B3GAT1), effectively blocks IBV infection. Subsequent studies reveal that B3GAT1 activity prevents cell surface sialic acid expression. Due to this mechanism of action, B3GAT1 expression broadly restricts infection with viruses that require sialic acid for entry, including Victoria and Yamagata lineage IBVs, H1N1/H3N2 influenza A viruses (IAVs), and the unrelated enterovirus D68. To understand the potential utility of B3GAT1 induction as an antiviral strategy in vivo, we specifically express B3GAT1 in the murine respiratory epithelium and find that overexpression is not only well-tolerated, but also protects female mice from a lethal viral challenge with multiple influenza viruses, including a pandemic-like H1N1 IAV. Thus, B3GAT1 may represent a host-directed broad-spectrum antiviral target with utility against clinically relevant respiratory viruses.

Novel Requirement for Staphylococcal Cell Wall-Anchored Protein SasD in Pulmonary Infection

Staphylococcus aureus can complicate preceding viral infections, including influenza virus. A bacterial infection combined with a preceding viral infection, known as superinfection, leads to worse outcomes than a single infection. Most of the pulmonary infection literature focuses on the changes in immune responses to bacteria between homeostatic and virally infected lungs. However, it is unclear how much of an influence bacterial virulence factors have in single or superinfection. Staphylococcal species express a broad range of cell wall-anchored proteins (CWAs) that have roles in host adhesion, nutrient acquisition, and immune evasion. We screened the importance of these CWAs using mutants lacking individual CWAs in vivo in both bacterial pneumonia and influenza superinfection. In bacterial pneumonia, the lack of individual CWAs leads to various decreases in bacterial burden, lung damage, and immune infiltration into the lung. However, the presence of a preceding influenza infection partially abrogates the requirement for CWAs. In the screen, we found that the uncharacterized CWA S. aureus surface protein D (SasD) induced changes in both inflammatory and homeostatic lung markers. We further characterized a SasD mutant (sasD A50.1) in the context of pneumonia. Mice infected with sasD A50.1 have decreased bacterial burden, inflammatory responses, and mortality compared to wild-type S. aureus. Mice also have reduced levels of interleukin-1β (IL-1β), likely derived from macrophages. Reductions in IL-1β transcript levels as well as increased macrophage viability point at differences in cell death pathways. These data identify a novel virulence factor for S. aureus that influences inflammatory signaling within the lung. IMPORTANCE Staphylococcus aureus is a common commensal bacterium that can cause severe infections, such as pneumonia. In the lung, viral infections increase the risk of staphylococcal pneumonia, leading to combined infections known as superinfections. The most common virus associated with S. aureus pneumonia is influenza, and superinfections lead to worse patient outcomes than either infection alone. While there is much known about how the immune system differs between healthy and virally infected lungs, the role of bacterial virulence factors in single and superinfection is less understood. The significance of our research is identifying bacterial components that play a role in the initiation of lung injury, which could lead to future therapies to prevent pulmonary single or superinfection with S. aureus.

A(H3N2) antigenic variation of influenza is associated with low vaccine efficacy in the early 2018 influenza season in Mexico City

OBJECTIVES

We evaluated the VE and the mutations of the viruses present in the Mexican population at the beginning of 2018.

METHODS

We diagnosed influenza in outpatients with a high-performance Rapid Influenza Diagnostic Test (RIDT) qRT-PCR. Descriptive statistics were used to describe the study population, while the chi-square test was used to determine clinical variables. VE was analyzed through a negative test design. We sequenced the hemagglutinin (HA) gene, performed a phylogenetic analysis, and analyzed the nonsynonymous substitutions both in and outside antigenic sites.

RESULTS

Of the 240 patients analyzed, 42.5% received the trivalent vaccine, and 37.5% were positive for influenza. The VE for the general population for any influenza virus type or subtype was 37.0%, while the VE for the predominant influenza A(H3N2) subtype was the lowest (19.7%). The phylogenetic analysis of HA showed the co-circulation of clades and subclades 3C.2a1, 3C.2a1b, 3C.2a2, 3C.2a2re, 3C.2a3, and 3C.3a with identities approximately 97-98% similar to the vaccine composition.

CONCLUSION

Low VE was related to the co-circulation of multiple clades and subclades of influenza A(H3N2), with sufficient genetic and phenotypic distance to allow for the infection of vaccinated individuals.

Harmonization and qualification of intracellular cytokine staining to measure influenza-specific CD4+ T cell immunity within the FLUCOP consortium

Despite the knowledge that cell-mediated immunity (CMI) contributes to the reduction of severe influenza infection, transmission, and disease outcome, the correlates of protection for cell-mediated immunity remain still unclear. Therefore, measuring the magnitude and quality of influenza-specific T cell responses in a harmonized way is of utmost importance to improve characterisation of vaccine-induced immunity across different clinical trials. The present study, conducted as part of the FLUCOP project, describes the development of a consensus protocol for the intracellular cytokine staining (ICS) assay, in order to reduce inter-laboratory variability, and its qualification. In order to develop a consensus protocol, the study was divided into different stages. Firstly, two pilot studies evaluated critical parameters in the analytical (read-outs) and post-analytical (gating strategies and data analysis) methods applied by eight different laboratories within the FLUCOP consortium. The methods were then harmonized by fixing the critical parameters and the subsequent consensus protocol was then qualified by one FLUCOP member. The antigen-specific cell population was defined as polypositive CD4⁺ T cells (i.e. positive for at least two markers among CD40L/IFNγ/IL2/TNFα), which was shown to be the most sensitive and specific read-out. The qualification of this consensus protocol showed that the quantification of polypositive CD4⁺ T cells was precise, linear and accurate, and sensitive with a lower limit of quantification of 0.0335% antigen-specific polypositive CD4⁺ T cells. In conclusion, we provide the description of a harmonized ICS assay, which permits quantitative and qualitative evaluation of influenza vaccine-induced T cell responses. Application of this harmonized assay may allow for future comparisons of T cell responses to different influenza vaccines. It may facilitate future assessments of potential correlates of protection with the promise of application across other pathogens.

Improving cross-protection against influenza virus in mice using a nanoparticle vaccine of mini-HA

This study aimed to investigate the protective effect of mini-hemagglutinin (mini-HA) proteins expressed on lumazine synthase (LS) nanoparticles against influenza. Soluble mini-HA proteins were assembled with LS proteins via SpyTag/SpyCatcher in vitro. The size of mini-HA-LS nanoparticles was characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and the effect of mini-HA-LS nano-vaccines was explored in mice. The results indicate that the diameter of mini-HA-LS nanoparticles was approximately 60-80 nm. The nanoparticles could induce stronger humoral and cellular immune responses and produce cross-clade protection against influenza in mice.

Association of functional competencies with vaccination among older adults: a JAGES cross-sectional study

It is unknown whether higher functions in sublevels of competence other than instrumental activities of daily living (IADL) are associated with vaccinations. This study examined whether higher functions, including intellectual activity (IA) and social role (SR), were associated with vaccinations among 26,177 older adults. Older adults with incapable activities in IA and SR had increased risks for non-receipt of influenza vaccinations (IA: for one incapable task/activity: incident rate ratio (IRR) = 1.05, 95% confidence interval (CI) = 1.02-1.09; SR: for two incapable tasks: IRR = 1.12, 95% CI = 1.08-1.16). Those with incapable activities in IADL and IA had increased risks for non-receipt of pneumococcal vaccination (IADL: for two incapable tasks: IRR = 1.13, 95% CI = 1.05-1.23; IA: for two incapable tasks: IRR = 1.10, 95% CI = 1.08-1.12). Those with incapable activities in IADL, IA, and SR had increased risks for non-receipt of both of the two vaccinations (IADL: for two incapable tasks: IRR = 1.17, 95% CI = 1.03-1.33; IA: for two incapable tasks: IRR = 1.18, 95% CI = 1.11-1.25; SR: for two incapable tasks: IRR = 1.13, 95% CI = 1.07-1.20). Having a family physician mitigated associations for non-receipt, regardless of competency. Our results suggest-maintaining the higher functions are important for older adults to undergo recommended vaccinations as scheduled; also, having a family physician to promote vaccinations is beneficial even for older adults with limited functions.

The evolutionary potential of influenza A virus hemagglutinin is highly constrained by epistatic interactions with neuraminidase

Antigenic evolution of the influenza A virus (IAV) hemagglutinin (HA) gene limits efforts to effectively control the spread of the virus in the population. Efforts to understand the mechanisms governing HA antigenic evolution typically examine the HA gene in isolation. This can ignore the importance of balancing HA receptor binding activities with the receptor-destroying activities of the viral neuraminidase (NA) to maintain viral fitness. We hypothesize that the need to maintain functional balance with NA significantly constrains the evolutionary potential of the HA. We use deep mutational scanning and show that variation in NA activity significantly reshapes the HA fitness landscape by modulating the overall mutational robustness of HA. Consistent with this, we observe that different NA backgrounds support the emergence of distinct repertoires of HA escape variants under neutralizing antibody pressure. Our results reveal a critical role for intersegment epistasis in influencing the evolutionary potential of the HA gene.

Immunodominance hierarchy after seasonal influenza vaccination

Current influenza vaccines elicit humoral immune responses against the hemagglutinin (HA) protein of influenza viruses. Different antigenic sites have been identified in the HA head as the main target of hemagglutination inhibition (HAI) antibodies (Sb, Sa, Cb, Ca1 and Ca2). To determine immunodominance (ID) of each site, we performed HAI assays against a panel of mutant viruses, each one lacking one of the classically defined antigenic sites and compared it to wild type (Wt). Agglutinating antibodies were measured before and after vaccination in two different regimens: Quadrivalent Influenza Vaccine (QIV) in young adults; or Adjuvanted Trivalent influenza Vaccine (ATIV) in elderly. Our results showed abs before vaccination were significantly reduced against all antigenic sites in the elderly and only against Sb and Ca2 in young adults compared to the Wt. Humoral response to vaccination was significantly reduced against all viruses compared to the Wt for the ATIV and only against Sb and Ca2 for the QIV. The strongest reduction was observed in all cases against Sb followed by Ca2. We concluded that ID profile was clearly dominated by Sb followed by Ca2. Additionally, the antibody response evolved with age, increasing the response towards less immunodominant epitopes of HA head. Adjuvants can positively influence ID hierarchy broadening responses towards multiple antigenic sites of HA head.

Dearth of influenza among older adults admitted with respiratory symptoms in Malaysia during the coronavirus disease 2019 pandemic in 2021

Introduction

Influenza is a common respiratory virus which leads to over 400,000 annual deaths globally. Mortality from influenza is highest among those aged 75 years and over living in Africa and Southeast Asia.

Objective

To determine the burden of influenza among older adults presenting to public hospitals with severe acute respiratory infection (SARI) during the coronavirus disease 2019 (COVID-19) pandemic.

Methods

This multi-center, prospective, observational study recruited individuals aged 65 years and over who presented to four Malaysian hospitals with SARI from 1 January to 31 December 2021. Those with prior confirmed severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection were excluded. SARS-CoV-2 was detected through real-time polymerase chain reaction (PCR) with routine diagnostic kits. Influenza A, influenza B and respiratory syncytial virus (RSV) viruses were detected with Xpress Flu/RSV kits using the GeneXpert rapid real-time PCR system (Cepheid, USA).

Results

Samples were obtained from 512 participants, comprising 296 (57.8%) men and 216 (42.2%) women, with a mean age (SD) of 74.0 (7.1) years. Inpatient death occurred in 48 (9.6%) individuals. Significant differences existed in age, ethnicity, and comorbidities across study sites. One (0.2%) case of influenza A, two (0.4%) cases of RSV and 63 (12.5%) cases of SARS-CoV-2 infection were detected over the 1-year period. Cases of COVID-19 mirrored national trends derived from open source data, while the dearth of influenza cases mirrored national and global Flunet figures.

Conclusion

Our observational study conducted during the COVID-19 pandemic detected only one case of influenza, alongside a high SARS-CoV-2 positivity rate. The poor uptake of influenza vaccination nationally, worsened by the recent pandemic restrictions, could lead to waning immunity from the absence of seasonal exposure. Potentially deadly outbreaks may then occur when lockdown and infection control measures are eventually removed.