Concomitant administration of seasonal influenza and COVID-19 mRNA vaccines

Current clinical guidelines support the concomitant administration of seasonal influenza vaccines and COVID-19 mRNA boosters vaccine. Whether dual vaccination may impact vaccine immunogenicity due to an interference between influenza or SARS-CoV-2 antigens is unknown. We aimed to understand the impact of mRNA COVID-19 vaccines administered concomitantly on the immune response to influenza vaccines. For this, 128 volunteers were vaccinated during the 22-23 influenza season. Three groups of vaccination were assembled: FLU vaccine only (46, 35%) versus volunteers that received the mRNA bivalent COVID-19 vaccines concomitantly to seasonal influenza vaccines, FluCOVID vaccine in the same arm (42, 33%) or different arm (40, 31%), respectively. Sera and whole blood were obtained the day of vaccination, +7, and +28 days after for antibody and T cells response quantification. As expected, side effects were increased in individuals who received the FluCOVID vaccine as compared to FLU vaccine only based on the known reactogenicity of mRNA vaccines. In general, antibody levels were high at 4 weeks post-vaccination and differences were found only for the H3N2 virus when administered in different arms compared to the other groups at day 28 post-vaccination. Additionally, our data showed that subjects that received the FluCOVID vaccine in different arm tended to have better antibody induction than those receiving FLU vaccines for H3N2 virus in the absence of pre-existing immunity. Furthermore, no notable differences in the influenza-specific cellular immune response were found for any of the vaccination groups. Our data supports the concomitant administration of seasonal influenza and mRNA COVID-19 vaccines.

Children with influenza admitted at a children's hospital in Argentina in the 2019-2022 period: What has changed after the COVID-19 pandemic?

Introduction. During 2020 and 2021, the circulation of influenza virus remained below expectations worldwide. In Argentina, in 2022, we observed an uninterrupted circulation of influenza all year round. Our objectives were to describe the circulation patterns and clinical characteristics of hospitalized children with influenza. Population and methods. Retrospective, analytical, observational study. All children with influenza virus admitted to a children's hospital during the 2019-2022 period were included. Results. A total of 138 patients were admitted over 4 years; in 2019, the rate of hospital discharges was 4.5/1000, compared to 15.1/1000 in 2022. No cases were recorded in 2020 and 2021. In 2019, most cases were observed in the winter; in 79%, the cause was acute lower respiratory tract infection (ALRTI); influenza A was detected in 92%. In 2022, most cases occurred in the spring; 62% developed ALRTI; and influenza A was detected in 56%. Similar rates of vaccination and comorbidities were observed in both periods. Conclusions. In 2022, more hospitalizations due to influenza were recorded, which may have correlated with the use of more sensitive molecular diagnostic testing and a change in seasonality, with more cases observed in the spring. In 2019, influenza A predominated in lower respiratory tract infections, while in 2022, cases of influenza A and B were similar, with more extra-pulmonary forms.

Influenza A virus antibodies in dogs, hunting dogs, and backyard pigs in Campeche, Mexico

AIMS

This study aimed to identify exposure to human, swine, and avian influenza A virus subtypes in rural companion and hunting dogs, backyard pigs, and feral pigs.

METHODS AND RESULTS

The study took place in a region of southeastern Mexico where the sampled individuals were part of backyard production systems in which different domestic and wild species coexist and interact with humans. We collected blood samples from pigs and dogs at each of the sites. We used a nucleoprotein enzyme-linked immunosorbent assay to determine the exposure of individuals to influenza A virus. Haemagglutination inhibition was performed on the positive samples to determine the subtypes to which they were exposed. For data analysis, a binomial logistic regression model was generated to determine the predictor variables for the seropositivity of the individuals in the study. We identified 11 positive individuals: three backyard pigs, four companion dogs, and four hunting dogs. The pigs tested positive for H1N1 and H1N2. The dogs were positive for H1N1, H1N2, and H3N2. The model showed that dogs in contact with backyard chickens are more likely to be seropositive for influenza A viruses.

CONCLUSIONS

We demonstrated the essential role hunting dogs could play as intermediate hosts and potential mixing vessel hosts when exposed to human and swine-origin viral subtypes. These results are relevant because these dogs interact with domestic hosts and humans in backyard systems, which are risk scenarios in the transmission of influenza A viruses. Therefore, it is of utmost importance to implement epidemiological surveillance of influenza A viruses in backyard animals, particularly in key animals in the transmission of these viruses, such as dogs and pigs.

Effects of high-dose versus standard-dose quadrivalent influenza vaccine among patients with diabetes: A post-hoc analysis of the DANFLU-1 trial

AIM

High-dose quadrivalent influenza vaccine (QIV-HD) has been shown to be more effective than standard-dose (QIV-SD) in reducing influenza infection, but whether diabetes status affects relative vaccine effectiveness (rVE) is unknown. We aimed to assess rVE on change in glycated haemoglobin [HbA1c (∆HbA1c)], incident diabetes, total all-cause hospitalizations (first + recurrent), and a composite of all-cause mortality and hospitalization for pneumonia or influenza.

METHODS

DANFLU-1 was a pragmatic, open-label trial randomizing adults (65-79 years) 1:1 to QIV-HD or QIV-SD during the 2021/22 influenza season. Cox proportional hazards regression was used to estimate rVE against incident diabetes and the composite endpoint, negative binomial regression to estimate rVE against all-cause hospitalizations, and ANCOVA when assessing rVE against ∆HbA1c.

RESULTS

Of the 12 477 participants, 1162 (9.3%) had diabetes at baseline. QIV-HD, compared with QIV-SD, was associated with a reduction in the rate of all-cause hospitalizations irrespective of diabetes [overall: 647 vs. 742 events, incidence rate ratio (IRR): 0.87, 95% CI (0.76-0.99); diabetes: 93 vs. 118 events, IRR: 0.80, 95% CI (0.55-1.15); without diabetes: 554 vs. 624 events, IRR: 0.88, 95% CI (0.76-1.01), pinteraction = 0.62]. Among those with diabetes, QIV-HD was associated with a lower risk of the composite outcome [2 vs. 11 events, HR: 0.18, 95% CI (0.04-0.83)] but had no effect on ∆HbA1c; QIV-HD adjusted mean difference: ∆ + 0.2 mmol/mol, 95% CI (-0.9 to 1.2). QIV-HD did not affect the risk of incident diabetes [HR 1.18, 95% CI (0.94-1.47)].

CONCLUSIONS

In this post-hoc analysis, QIV-HD versus QIV-SD was associated with an increased rVE against the composite of all-cause death and hospitalization for pneumonia/influenza, and the all-cause hospitalization rate irrespective of diabetes status.

Live-attenuated virus vaccine defective in RNAi suppression induces rapid protection in neonatal and adult mice lacking mature B and T cells

Global control of infectious diseases depends on the continuous development and deployment of diverse vaccination strategies. Currently available live-attenuated and killed virus vaccines typically take a week or longer to activate specific protection by the adaptive immunity. The mosquito-transmitted Nodamura virus (NoV) is attenuated in mice by mutations that prevent expression of the B2 viral suppressor of RNA interference (VSR) and consequently, drastically enhance in vivo production of the virus-targeting small-interfering RNAs. We reported recently that 2 d after immunization with live-attenuated VSR-disabled NoV (NoVΔB2), neonatal mice become fully protected against lethal NoV challenge and develop no detectable infection. Using Rag1-/- mice that produce no mature B and T lymphocytes as a model, here we examined the hypothesis that adaptive immunity is dispensable for the RNAi-based protective immunity activated by NoVΔB2 immunization. We show that immunization of both neonatal and adult Rag1-/- mice with live but not killed NoVΔB2 induces full protection against NoV challenge at 2 or 14 d postimmunization. Moreover, NoVΔB2-induced protective antiviral immunity is virus-specific and remains effective in adult Rag1-/- mice 42 and 90 d after a single-shot immunization. We conclude that immunization with the live-attenuated VSR-disabled RNA virus vaccine activates rapid and long-lasting protective immunity against lethal challenges by a distinct mechanism independent of the adaptive immunity mediated by B and T cells. Future studies are warranted to determine whether additional animal and human viruses attenuated by VSR inactivation induce similar protective immunity in healthy and adaptive immunity-compromised individuals.

Generation of Broad Protection against Influenza with Di-Tyrosine-Cross-Linked M2e Nanoclusters

Tyrosine cross-linking has recently been used to produce nanoclusters (NCs) from peptides to enhance their immunogenicity. In this study, NCs were generated using the ectodomain of the ion channel Matrix 2 (M2e) protein, a conserved influenza surface antigen. The NCs were administered via intranasal (IN) or intramuscular (IM) routes in a mouse model in a prime-boost regimen in the presence of the adjuvant CpG. After boost, a significant increase in anti-M2e IgG and its subtypes was observed in the serum and lungs of mice vaccinated through the IM and IN routes; however, significant enhancement in anti-M2e IgA in lungs was observed only in the IN group. Analysis of cytokine concentrations in stimulated splenocyte cultures indicated a Th1/Th17-biased response. Mice were challenged with a lethal dose of A/California/07/2009 (H1N1pdm), A/Puerto Rico/08/1934 (H1N1), or A/Hong Kong/08/1968 (H3N2) strains. Mice that received M2e NCs + CpG were significantly protected against these strains and showed decreased lung viral titers compared with the naive mice and M2e NC-alone groups. The IN-vaccinated group showed superior protection against the H3N2 strain as compared to the IM group. This research extends our earlier efforts involving the tyrosine-based cross-linking method and highlights the potential of this technology in enhancing the immunogenicity of short peptide immunogens.

The host transcriptional response to superinfection by influenza A virus and Streptococcus pneumoniae

Secondary bacterial challenges during influenza virus infection "superinfection") cause excessive mortality and hospitalization. Here, we present a longitudinal study of bulk gene expression changes in murine lungs during superinfection, with an initial influenza A virus infection and a subsequent Streptococcus pneumoniae infection. In addition to the well-characterized impairment of the host response, we identified superinfection-specific alterations in the global transcriptional program that are linked to the host's ability to resist the pathogens. Particularly, whereas superinfected mice manifested an excessive rapid induction of the resistance-to-infection program, there was a substantial tissue-level rewiring of this program: upon superinfection, interferon-regulated genes were switched from positive to negative correlations with the host's resistance state, whereas genes of fatty acid metabolism switched from negative to positive correlations with resistance states. Thus, the transcriptional resistance state in superinfection is reprogrammed toward repressed interferon signaling and induced fatty acid metabolism. Our findings suggest new insights into a tissue-level remodeling of the host defense upon superinfection, providing promising targets for future therapeutic interventions.

IMPORTANCE

Secondary bacterial infections are the most frequent complications during influenza A virus (IAV) pandemic outbreaks, contributing to excessive morbidity and mortality in the human population. Most IAV-related deaths are attributed to Streptococcus pneumoniae (SP) infections, which usually begin within the first week of IAV infection in the respiratory tracts. Here, we focused on longitudinal transcriptional responses during a superinfection model consisting of an SP infection that follows an initial IAV infection, comparing superinfection to an IAV-only infection, an SP-only infection, and control treatments. Our longitudinal data allowed a fine analysis of gene expression changes during superinfection. For instance, we found that superinfected mice exhibited rapid gene expression induction or reduction within the first 12 h after encountering the second pathogen. Cell proliferation and immune response activation processes were upregulated, while endothelial processes, vasculogenesis, and angiogenesis were downregulated, providing promising targets for future therapeutic interventions. We further analyzed the longitudinal transcriptional responses in the context of a previously defined spectrum of the host's resistance state, revealing superinfection-specific reprogramming of resistance states, such as reprogramming of fatty acid metabolism and interferon signaling. The reprogrammed functions are compelling new targets for switching the pathogenic superinfection state into a single-infection state.

Prospective external validation of the FluScore risk score for influenza in outpatients

BACKGROUND

Testing for influenza in patients with acute lower respiratory tract infection (LRTI) is common and in some cases is performed for all patients with LRTI. A more selective approach to testing could be more efficient.

METHODS

We used data from two prospective studies in the US primary and urgent care settings that enrolled patients with acute LRTI or influenza-like illness. Data were collected in the 2016, 2019, 2021, and 2022 flu seasons. All patients underwent polymerase chain reaction (PCR) testing for influenza and the FluScore was calculated based on patient-reported symptoms at their initial visit. The probability of influenza in each risk group was reported, as well as stratum-specific likelihood ratios (SSLRs) for each risk level.

RESULTS

The prevalence of influenza within risk groups varied based on overall differences in flu seasons and populations. However, the FluScore exhibited consistent performance across various seasons and populations based on the SSLRs. The FluScore had a consistent SSLR range of 0.20 to 0.23 for the low-risk group, 0.63 to 0.99 for the moderate-risk group, and 1.46 to 1.67 for the high-risk group. The diagnostic odds ratio based on the midpoints of these ranges was 7.25.

CONCLUSIONS

The FluScore could streamline patient categorization, identifying patients who could be exempted from testing, while identifying candidates for rapid influenza tests. This has the potential to be more efficient than a "one size fits all" test strategy, as it strategically targets the use of tests on patients most likely to benefit. It is potentially usable in a telehealth setting.

Interaction and Antiviral Treatment of Coinfection between SARS-CoV-2 and Influenza in Vitro

BACKGROUND

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has lasted for three years. Coinfection with seasonal influenza may occur resulting in more severe diseases. The interaction between these two viruses for infection and the effect of antiviral treatment remains unclear.

METHODS

A SARS-CoV-2 and influenza H1N1 coinfection model on Calu-3 cell line was established, upon which the simultaneous and sequential coinfection was evaluated by comparing the viral load. The efficacy of molnupiravir and baloxavir against individual virus and coinfection were also studied.

RESULTS

The replication of SARS-CoV-2 was significantly interfered when the influenza virus was infected simultaneously or in advance (p<0.05). On the contrary, the replication of the influenza virus was not affected by the SARS-CoV-2. Molnupiravir monotherapy had significant inhibitory effect on SARS-CoV-2 when the concentration reached to 6.25μM but did not show any significant anti-influenza activity. Baloxavir was effective against influenza within the dosage range and showed significant effect of anti-SARS-CoV-2 at 16μM. In the treatment of coinfection, molnupiravir had significant effect for SARS-CoV-2 from 6.25μM to 100μM and inhibited H1N1 at 100μM (p<0.05). The tested dosage range of baloxavir can inhibit H1N1 significantly (p<0.05), while at the highest concentration of baloxavir did not further inhibit SARS-CoV-2, and the replication of SARS-CoV-2 significantly increased in lower concentrations. Combination treatment can effectively inhibit influenza H1N1 and SARS-CoV-2 replication during coinfection. Compared with molnupiravir or baloxavir monotherapy, combination therapy was more effective in less dosage to inhibit the replication of both viruses.

CONCLUSIONS

In coinfection, the replication of SARS-CoV-2 would be interfered by influenza H1N1. Compared with molnupiravir or baloxavir monotherapy, treatment with a combination of molnupiravir and baloxavir should be considered for early treatment in patients with SARS-CoV-2 and influenza coinfection.

Pathogenesis and Transmission Assessment of 3 Swine-Origin Influenza A(H3N2) Viruses With Zoonotic Risk to Humans Isolated in the United States, 2017-2020

The sporadic occurrence of human infections with swine-origin influenza A(H3N2) viruses and the continual emergence of novel A(H3N2) viruses in swine herds underscore the necessity for ongoing assessment of the pandemic risk posed by these viruses. Here, we selected 3 recent novel swine-origin A(H3N2) viruses isolated between 2017 to 2020, bearing hemagglutinins from the 1990.1, 2010.1, or 2010.2 clades, and evaluated their ability to cause disease and transmit in a ferret model. We conclude that despite considerable genetic variances, all 3 contemporary swine-origin A(H3N2) viruses displayed a capacity for robust replication in the ferret respiratory tract and were also capable of limited airborne transmission. These findings highlight the continued public health risk of swine-origin A(H3N2) strains, especially in human populations with low cross-reactive immunity.

An infant mouse model of influenza-driven nontypeable Haemophilus influenzae colonization and acute otitis media suitable for preclinical testing of novel therapies

Nontypeable Haemophilus influenzae (NTHi) is a major otitis media (OM) pathogen, with colonization a prerequisite for disease development. Most acute OM is in children <5 years old, with recurrent and chronic OM impacting hearing and learning. Therapies to prevent NTHi colonization and/or disease are needed, especially for young children. Respiratory viruses are implicated in driving the development of bacterial OM in children. We have developed an infant mouse model of influenza-driven NTHi OM, as a preclinical tool for the evaluation of safety and efficacy of clinical therapies to prevent NTHi colonization and the development of OM. In this model, 100% of infant BALB/cARC mice were colonized with NTHi, and all developed NTHi OM. Influenza A virus (IAV) facilitated the establishment of dense (1 × 105 CFU/mL) and long-lasting (6 days) NTHi colonization. IAV was essential for the development of NTHi OM, with 100% of mice in the IAV/NTHi group developing NTHi OM compared with 8% of mice in the NTHi only group. Histological analysis and cytokine measurements revealed that the inflammation observed in the middle ear of the infant mice with OM reflected inflammation observed in children with OM. We have developed the first infant mouse model of NTHi colonization and OM. This ascension model uses influenza-driven establishment of OM and reflects the clinical pathology of bacterial OM developing after a respiratory virus infection. This model provides a valuable tool for testing therapies to prevent or treat NTHi colonization and disease in young children.

Age-Specific Resurgence in Invasive Pneumococcal Disease Incidence in the COVID-19 Pandemic Era and Its Association With Respiratory Virus and Pneumococcal Carriage Dynamics: A Time-Series Analysis

Using multiple national surveillance systems, we found an increase in the incidence of invasive pneumococcal disease during after the relaxation of non-pharmaceutical interventions against COVID-19, which strongly varied by age. Age groups with higher incidence of respiratory syncytial virus and influenza also experienced higher increase in invasive pneumococcal disease incidence, with no change in pneumococcal carriage.

Vaccine Effectiveness Against Influenza A-Associated Hospitalization, Organ Failure, and Death: United States, 2022-2023

BACKGROUND

Influenza circulation during the 2022-2023 season in the United States largely returned to pre-coronavirus disease 2019 (COVID-19)-pandemic patterns and levels. Influenza A(H3N2) viruses were detected most frequently this season, predominately clade 3C.2a1b.2a, a close antigenic match to the vaccine strain.

METHODS

To understand effectiveness of the 2022-2023 influenza vaccine against influenza-associated hospitalization, organ failure, and death, a multicenter sentinel surveillance network in the United States prospectively enrolled adults hospitalized with acute respiratory illness between 1 October 2022, and 28 February 2023. Using the test-negative design, vaccine effectiveness (VE) estimates against influenza-associated hospitalization, organ failures, and death were measured by comparing the odds of current-season influenza vaccination in influenza-positive case-patients and influenza-negative, SARS-CoV-2-negative control-patients.

RESULTS

A total of 3707 patients, including 714 influenza cases (33% vaccinated) and 2993 influenza- and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-negative controls (49% vaccinated) were analyzed. VE against influenza-associated hospitalization was 37% (95% confidence interval [CI]: 27%-46%) and varied by age (18-64 years: 47% [30%-60%]; ≥65 years: 28% [10%-43%]), and virus (A[H3N2]: 29% [6%-46%], A[H1N1]: 47% [23%-64%]). VE against more severe influenza-associated outcomes included: 41% (29%-50%) against influenza with hypoxemia treated with supplemental oxygen; 65% (56%-72%) against influenza with respiratory, cardiovascular, or renal failure treated with organ support; and 66% (40%-81%) against influenza with respiratory failure treated with invasive mechanical ventilation.

CONCLUSIONS

During an early 2022-2023 influenza season with a well-matched influenza vaccine, vaccination was associated with reduced risk of influenza-associated hospitalization and organ failure.

Outcomes of SARS-CoV-2 Omicron Variant Infections Compared With Seasonal Influenza and Respiratory Syncytial Virus Infections in Adults Attending the Emergency Department: A Multicenter Cohort Study

BACKGROUND

There is a controversy over the impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in an era of less virulent variants and an increasing population immunity. We compared outcomes in adults attending the emergency department (ED) with an Omicron, influenza, or respiratory syncytial virus (RSV) infection.

METHODS

Retrospective multicenter cohort study including adults attending the ED in 6 acute care hospitals in Stockholm County, Sweden, with an Omicron, influenza, or RSV infection during 2021-2022 and 2015-2019. During 2021-2022, patients were tested for all 3 viruses by multiplex polymerase chain reaction (PCR) testing. The primary outcome was 30-day all-cause mortality. Secondary outcomes were 90-day all-cause mortality, hospitalization, and intensive care unit (ICU) admission.

RESULTS

A total of 6385 patients from 2021-2022 were included in the main analyses: 4833 Omicron, 1099 influenza, and 453 RSV. The 30-day mortality was 7.9% (n = 381) in the Omicron, 2.5% (n = 28) in the influenza, and 6.0% (n = 27) in the RSV cohort. Patients with Omicron had an adjusted 30-day mortality odds ratio (OR) of 2.36 (95% confidence interval [CI] 1.60-3.62) compared with influenza and 1.42 (95% CI .94-2.21) compared with RSV. Among unvaccinated Omicron patients, stronger associations were observed compared with both influenza (OR 5.51 [95% CI 3.41-9.18]) and RSV (OR 3.29 [95% CI 2.01-5.56]). Similar trends were observed for secondary outcomes. Findings were consistent in comparisons with 5709 pre-pandemic influenza 995 RSV patients.

CONCLUSIONS

In patients attending the ED, infections with Omicron were both more common and associated with more severe outcomes compared with influenza and RSV, in particular among unvaccinated patients.

High-pathogenicity avian influenza in wildlife: a changing disease dynamic that is expanding in wild birds and having an increasing impact on a growing number of mammals

While diverse strains of low-pathogenicity avian influenza have circulated in wild birds for a long period of time, there has previously been little pathology in wild birds, ducks have been the primary and largely asymptomatic wild reservoir, and spillover into mammals has been limited and rare. In recent years, a high-pathogenicity avian influenza (HPAI) virus has emerged on the global scene and shifted the previously established dogmas for influenza infection. High-pathogenicity avian influenza has expanded into wildlife in unprecedented numbers and species diversity, with unmatched disease severity for influenza in wildlife. As the disease ecology of influenza has shifted with this new variant, significant efforts are underway to understand disease course, pathology, and species susceptibility. Here we focus primarily on the impact that HPAI has had in wild mammals while framing these novel spillovers within the context of significantly expanding disease in avian species and geography. The clinical and pathology presentations of HPAI in these atypical hosts are discussed, as well as prognosis and risk for continued spillover. The companion Currents in One Health by Runstadler and Puryear, AJVR, May 2024, provides further context on viral reservoirs and possible routes of direct or environmental transmission and risk assessment of viral variants that are emerging within wildlife.

Feruloylated Oligosaccharides Prevented Influenza-Induced Lung Inflammation via the RIG-I/MAVS/TRAF3 Pathway

Uncontrolled inflammation contributes significantly to the mortality in acute respiratory infections. Our previous research has demonstrated that maize bran feruloylated oligosaccharides (FOs) possess notable anti-inflammatory properties linked to the NF-kB pathway regulation. In this study, we clarified that the oral administration of FOs moderately inhibited H1N1 virus infection and reduced lung inflammation in influenza-infected mice by decreasing a wide spectrum of cytokines (IFN-α, IFN-β, IL-6, IL-10, and IL-23) in the lungs. The mechanism involves FOs suppressing the transduction of the RIG-I/MAVS/TRAF3 signaling pathway, subsequently lowering the expression of NF-κB. In silico analysis suggests that FOs have a greater binding affinity for the RIG-I/MAVS signaling complex. This indicates that FOs have potential as promising targets for immune modulation. Moreover, in MAVS knockout mice, we confirmed that the anti-inflammatory function of FOs against influenza depends on MAVS. Comprehensive analysis using 16S rRNA gene sequencing and metabolite profiling techniques showed that FOs have the potential to restore immunity by modulating the gut microbiota. In conclusion, our study demonstrates that FOs are effective anti-inflammatory phytochemicals in inhibiting lung inflammation caused by influenza. This suggests that FOs could serve as a potential nutritional strategy for preventing the H1N1 virus infection and associated lung inflammation.

Relative Role of Age Groups and Indoor Environments in Influenza Transmission Under Different Urbanization Rates in China

Exploring the relative role of different indoor environments in respiratory infections transmission remains unclear, which is crucial for developing targeted nonpharmaceutical interventions. In this study, a total of 2,583,441 influenza-like illness cases tested from 2010 to 2017 in China were identified. An agent-based model was built and calibrated with the surveillance data, to assess the roles of 3 age groups (children <19 years, younger adults 19-60 years, older adults >60 years) and 4 types of indoor environments (home, schools, workplaces, and community areas) in influenza transmission by province with varying urbanization rates. When the urbanization rates increased from 35% to 90%, the proportion of children aged <19 years among influenza cases decreased from 76% to 45%. Additionally, we estimated that infections originating from children decreased from 95.1% (95% confidence interval (CI): 92.7, 97.5) to 59.3% (95% CI: 49.8, 68.7). Influenza transmission in schools decreased from 80.4% (95% CI: 76.5, 84.3) to 36.6% (95% CI: 20.6, 52.5), while transmission in the community increased from 2.4% (95% CI: 1.9, 2.8) to 45.4% (95% CI: 35.9, 54.8). With increasing urbanization rates, community areas and younger adults contributed more to infection transmission. These findings could help the development of targeted public health policies. This article is part of a Special Collection on Environmental Epidemiology. This article is part of a Special Collection on Environmental Epidemiology.

Decreased risk of non-influenza respiratory infection after influenza B virus infection in children

Previous studies suggest that influenza virus infection may provide temporary non-specific immunity and hence lower the risk of non-influenza respiratory virus infection. In a randomized controlled trial of influenza vaccination, 1 330 children were followed-up in 2009-2011. Respiratory swabs were collected when they reported acute respiratory illness and tested against influenza and other respiratory viruses. We used Poisson regression to compare the incidence of non-influenza respiratory virus infection before and after influenza virus infection. Based on 52 children with influenza B virus infection, the incidence rate ratio (IRR) of non-influenza respiratory virus infection after influenza virus infection was 0.47 (95% confidence interval: 0.27-0.82) compared with before infection. Simulation suggested that this IRR was 0.87 if the temporary protection did not exist. We identified a decreased risk of non-influenza respiratory virus infection after influenza B virus infection in children. Further investigation is needed to determine if this decreased risk could be attributed to temporary non-specific immunity acquired from influenza virus infection.

Unveiling the role of preceding seasonal influenza in the development of bacteremic pneumococcal pneumonia in older adults before the COVID-19 pandemic in Japan

OBJECTIVE

We aimed to investigate the impact of preceding seasonal influenza on the clinical characteristics of adult patients with invasive pneumococcal disease (IPD) in Japan.

METHODS

Data for 1,722 adult patients with IPD were analyzed before (2017-2019) and during the COVID-19 pandemic (2020-2022).

RESULTS

Seasonal influenza epidemic disappeared soon after the emergence of the pandemic. Compared with that before the pandemic (66.7%), we observed a lower bacteremic pneumonia proportion in patients with IPD during the pandemic (55.6%). The clinical presentations of IPD cases significantly differed between those with and without preceding influenza. The proportion of bacteremic pneumonia was higher in IPD patients with preceding influenza than in those without in both younger (44.9% vs. 84.2%) and older adults (65.5% vs. 87.0%) before the pandemic. The case fatality rate was significantly higher in IPD patients with preceding influenza (28.3%) than in those without (15.3%) in older adults before the pandemic (P = 0.020). Male and aging are high risk factors for death in older patients with IPD who had preceding influenza.

CONCLUSION

Our study reveals that preceding seasonal influenza plays a role in the development of bacteremic pneumococcal pneumonia, increasing the risk of death in older adults.

Alveolar epithelial cells of lung fibrosis patients are susceptible to severe virus-induced injury

Patients with pulmonary fibrosis (PF) often experience exacerbations of their disease, characterised by a rapid, severe deterioration in lung function that is associated with high mortality. Whilst the pathobiology of such exacerbations is poorly understood, virus infection is a trigger.  This study investigated virus-induced injury responses of alveolar and bronchial epithelial cells (AECs and BECs respectively) from patients with PF and age-matched controls (Ctrls).  Air liquid interface (ALI) cultures of AECs, comprising type I and II pneumocytes or BECs were inoculated with influenza A virus (H1N1) at 0.1 multiplicity of infection (MOI).  Levels of interleukin-6 (IL-6), IL-36γ and IL-1β were elevated in cultures of AECs from PF patients (PF-AECs, n=8-11), being markedly higher than Ctrl-AECs (n=5-6), 48 h post inoculation (pi) (P<0.05); despite no difference in H1N1 RNA copy numbers 24 h pi.  Furthermore, the virus-induced inflammatory responses of PF-AECs were greater than BECs (from either PF patients or controls), even though viral loads in the BECs were overall 2 to 3-fold higher than AECs.  Baseline levels of the senescence and DNA damage markers, nuclear p21, p16 and H2AXγ were also significantly higher in PF-AECs than Ctrl-AECs and further elevated post-infection.  Senescence induction using etoposide augmented virus-induced injuries in AECs (but not viral load), whereas selected senotherapeutics (rapamycin and mitoTEMPO) were protective.  This study provides evidence that senescence increases the susceptibility of AECs from PF patients to severe virus-induced injury and suggests targeting senescence may provide an alternative option to prevent or treat the exacerbations that worsen the underlying disease.

A phase 1 study in healthy volunteers to investigate the safety, tolerability, and pharmacokinetics of VIR-2482: a monoclonal antibody for the prevention of severe influenza A illness

The objective of this study was to evaluate the safety, tolerability, pharmacokinetics (PK), and immunogenicity of VIR-2482 in healthy adult subjects. A phase 1, first-in-human, randomized, double-blind, placebo-controlled dose-escalation study was conducted. One hundred participants were allocated to four cohorts (60 mg, 300 mg, 1,200 mg, and 1,800 mg). In each cohort, participants were randomized in a 4:1 ratio (active:placebo) to receive either VIR-2482 or volume-matched placebo by gluteal intramuscular injection. Participants remained at the investigative site under observation for 48 h, and adverse events (AEs) were collected for 56 days. PK and immunogenicity were measured up to 52 weeks post-dose. VIR-2482 was well tolerated at all doses studied. The overall incidence of AEs was comparable between VIR-2482 (68.8%) and placebo (85.0%). Nineteen VIR-2482 (23.8%) and six placebo (30.0%) recipients had Grade 1 or 2 AEs that were considered to be related to the study intervention. There were no treatment-related serious AEs. Injection-site reactions (ISRs) were reported in six (7.5%) VIR-2482 recipients, while no such reactions were reported among the placebo recipients. All ISRs were Grade 1, and there was no relationship with the dose. Median VIR-2482 serum elimination half-life ranged from 56.7 to 70.6 days across cohorts. The serum area under the curve and Cmax were dose-proportional. Nasopharyngeal VIR-2482 concentrations were approximately 2%-5% of serum levels and were less than dose-proportional. The incidence of immunogenicity across all cohorts was 1.3%. Overall, the safety, tolerability, and pharmacokinetic profile of VIR-2482 at doses up to 1,800 mg supported its further investigation as a long-acting antibody for the prevention of influenza A illness. This study has been registered at ClinicalTrials.gov under identifier NCT04033406.

Impact of influenza related hospitalization in Spain: characteristics and risk factor of mortality during five influenza seasons (2016 to 2021)

Background

Estimating the global influenza burden in terms of hospitalization and death is important for optimizing prevention policies. Identifying risk factors for mortality allows for the design of strategies tailored to groups at the highest risk. This study aims to (a) describe the clinical characteristics of hospitalizations with a diagnosis of influenza over five flu seasons (2016-2017 to 2020-2021), (b) assess the associated morbidity (hospitalization rates and ICU admissions rate), mortality and cost of influenza hospitalizations in different age groups and (c) analyze the risk factors for mortality.

Methods

This retrospective study included all hospital admissions with a diagnosis of influenza in Spain for five influenza seasons. Data were extracted from the Spanish National Surveillance System for Hospital Data from 1 July 2016 to 30 June 2021. We identified cases coded as having influenza as a primary or secondary diagnosis (International Classification of Diseases, 10th revision, J09-J11). The hospitalization rate was calculated relative to the general population. Independent predictors of mortality were identified using multivariable logistic regression.

Results

Over the five seasons, there were 127,160 hospitalizations with a diagnosis of influenza. The mean influenza hospitalization rate varied from 5/100,000 in 2020-2021 (COVID-19 pandemic) to 92.9/100,000 in 2017-2018. The proportion of influenza hospitalizations with ICU admission was 7.4% and was highest in people aged 40-59 years (13.9%). The case fatality rate was 5.8% overall and 9.4% in those aged 80 years or older. Median length of stay was 5 days (and 6 days in the oldest age group). In the multivariable analysis, independent risk factors for mortality were male sex (odds ratio [OR] 1.14, 95% confidence interval [95% CI] 1.08-1.20), age (<5 years: OR 1; 5-19 years: OR 2.02, 95%CI 1.17-3.49; 20-39 years: OR 4.11, 95% CI 2.67-6.32; 40-59 years: OR 8.15, 95% CI 5.60-11.87; 60-79 years: OR 15.10, 95% CI 10.44-21.84; ≥80 years: OR 33.41, 95% CI 23.10-48.34), neurological disorder (OR 1.97, 95% CI 1.83-2.11), heart failure (OR 1.85, 95% CI 1.74-1.96), chronic kidney disease (OR 1.33, 95% CI 1.25-1.41), chronic liver disease (OR 2.95, 95% CI 2.68-3.27), cancer (OR 1.85, 95% CI 1.48-2.24), coinfection with SARS-CoV2 (OR 3.17, 95% CI 2.34-4.28), influenza pneumonia (OR 1.76, 95% CI 1.66-1.86) and admission to intensive care (OR 7.81, 95% CI 7.31-8.36).

Conclusion

Influenza entails a major public health burden. People aged over 60-and especially those over 80-show the longest hospital stays. Age is also the most significant risk factor for mortality, along with certain associated comorbidities.

Structural and functional characterization of the interaction between the influenza A virus RNA polymerase and the CTD of host RNA polymerase II

Influenza A viruses, causing seasonal epidemics and occasional pandemics, rely on interactions with host proteins for their RNA genome transcription and replication. The viral RNA polymerase utilizes host RNA polymerase II (Pol II) and interacts with the serine 5 phosphorylated (pS5) C-terminal domain (CTD) of Pol II to initiate transcription. Our study, using single-particle electron cryomicroscopy (cryo-EM), reveals the structure of the 1918 pandemic influenza A virus polymerase bound to a synthetic pS5 CTD peptide composed of four heptad repeats mimicking the 52 heptad repeat mammalian Pol II CTD. The structure shows that the CTD peptide binds at the C-terminal domain of the PA viral polymerase subunit (PA-C) and reveals a previously unobserved position of the 627 domain of the PB2 subunit near the CTD. We identify crucial residues of the CTD peptide that mediate interactions with positively charged cavities on PA-C, explaining the preference of the viral polymerase for pS5 CTD. Functional analysis of mutants targeting the CTD-binding site within PA-C reveals reduced transcriptional function or defects in replication, highlighting the multifunctional role of PA-C in viral RNA synthesis. Our study provides insights into the structural and functional aspects of the influenza virus polymerase-host Pol II interaction and identifies a target for antiviral development.IMPORTANCEUnderstanding the intricate interactions between influenza A viruses and host proteins is crucial for developing targeted antiviral strategies. This study employs advanced imaging techniques to uncover the structural nuances of the 1918 pandemic influenza A virus polymerase bound to a specific host protein, shedding light on the vital process of viral RNA synthesis. The study identifies key amino acid residues in the influenza polymerase involved in binding host polymerase II (Pol II) and highlights their role in both viral transcription and genome replication. These findings not only deepen our understanding of the influenza virus life cycle but also pinpoint a potential target for antiviral development. By elucidating the structural and functional aspects of the influenza virus polymerase-host Pol II interaction, this research provides a foundation for designing interventions to disrupt viral replication and transcription, offering promising avenues for future antiviral therapies.

Antiviral activity of adenoviral vector expressing human interferon lambda-4 against influenza virus

Interferon lambda (IFNλ), classified as a type III IFN, is a representative cytokine that plays an important role in innate immunity along with type I IFN. IFNλ can elicit antiviral states by inducing peculiar sets of IFN-stimulated genes (ISGs). In this study, an adenoviral vector expression system with a tetracycline operator system was used to express human IFNλ4 in cells and mice. The formation of recombinant adenovirus (rAd-huIFNλ4) was confirmed using immunohistochemistry assays and transmission electron microscopy. Its purity was verified by quantifying host cell DNA and host cell proteins, as well as by confirming the absence of the replication-competent adenovirus. The transduction of rAd-huIFNλ4 induced ISGs and inhibited four subtypes of the influenza virus in both mouse-derived (LA-4) and human-derived cells (A549). The antiviral state was confirmed in BALB/c mice following intranasal inoculation with 109 PFU of rAd-huIFNλ4, which led to the inhibition of four subtypes of the influenza virus in mouse lungs, with reduced inflammatory lesions. These results imply that human IFNλ4 could induce antiviral status by modulating ISG expression in mice.

Acceptance of Seasonal Influenza Vaccine Following COVID-19 Vaccination: A Survey among Israel Defense Forces Soldiers

Data regarding the contribution of COVID-19 vaccine rollouts to real-world uptake of influenza vaccination remains unclear. This cross-sectional survey-based study among Israel Defense Forces (IDF) soldiers aimed to assess the impact of the COVID-19 pandemic and specifically, previous COVID-19 vaccines uptake, on the intention to vaccinate for influenza during 2021-2022 season. Participants engaged in an online survey addressing vaccination history and current vaccine-related preferences. The survey was delivered prior to the initiation of the IDF's annual influenza immunization campaign. A multinomial logistic regression model was applied to analyze factors correlated with unwillingness to receive influenza vaccine. Overall, 825 invitations to participate in the survey were distributed and the overall response rate was 78.5%. Among the 648 participants who replied (61.6% males, median age of 20 years), 51.9% were willing to receive the upcoming influenza vaccine. Factors associated with vaccine reluctance included being female, not receiving the previous season's influenza vaccine, not having a previous diagnosis of COVID-19, and having decreased uptake of COVID-19 vaccines. Among participants not intending to receive an influenza vaccine, 50.3% stated that they are healthy and have no need for the vaccine and 36.2% stated they received too many vaccines over the previous year. The results of this study may suggest that influenza vaccination rates in the post-COVID-19 vaccine era may be reduced due to a perceived "vaccine saturation" phenomenon, owing to the density of COVID-19 vaccine administration. Future interventions such as campaigns related to maximizing influenza vaccination coverage should address repeated doses of COVID-19 vaccine administration.

Highly Pathogenic Avian Influenza A(H5N1) Viruses from Multispecies Outbreak, Argentina, August 2023

We report full-genome characterization of highly pathogenic avian influenza A(H5N1) clade 2.3.4.4b virus from an outbreak among sea lions (August 2023) in Argentina and possible spillover to fur seals and terns. Mammalian adaptation mutations in virus isolated from marine mammals and a human in Chile were detected in mammalian and avian hosts.

Testing pulmonary physiology in ventilated non-human primates

BACKGROUND

Animal models of respiratory viral infections are essential for investigating disease pathogenesis and the efficacy of antivirals and vaccine candidates. A major limitation in the research of respiratory diseases in animal models is correlating clinically relevant changes in pulmonary physiology with cellular and molecular mechanistic studies. Few animal models have captured and correlated physiologic changes in lung function and immune response within same experiment, which is critical given the heterogeneous nature of lung disease due to viral infections. In ventilated human patients, pulmonary physiology testing can be used to not only capture oxygenation, ventilation, but also pulmonary mechanics to yield quantitative measures of lung function and scalar tracings of flow-volume and pressure-volume loops. Application of this protocol during mechanical ventilation in non-human (NHP) models would represent a major advance in respiratory viral disease research.

METHODS

We have applied and optimized a human pulmonary physiology testing protocol to ventilated pigtail macaques (Macaca nemestrina) at baseline and 5 days after influenza A (IAV) viral inoculation.

RESULTS

The NHPs manifested clinical disease with hypothermia and loss of body weight. Declines in lung function were striking with a 66%-81% decline in P/F ratio, a measure of oxygenation reflecting the ratio of partial pressure of oxygen in arterial blood (PaO2 ) to the fraction of inspiratory oxygen concentration (FiO2 ). There was also a 16%-45% decline in lung compliance.

CONCLUSION

We describe a new approach to performing pulmonary physiology testing protocol in non-human primates to better capture quantitative correlates of respiratory disease and demonstrate protection by therapeutics and vaccines.

Validity of ICD-10-based algorithms to identify patients with influenza in inpatient and outpatient settings

PURPOSE

To evaluate the validity of ICD-10-CM code-based algorithms as proxies for influenza in inpatient and outpatient settings in the USA.

METHODS

Administrative claims data (2015-2018) from the largest commercial insurer in New Jersey (NJ), USA, were probabilistically linked to outpatient and inpatient electronic health record (EHR) data containing influenza test results from a large NJ health system. The primary claims-based algorithms defined influenza as presence of an ICD-10-CM code for influenza, stratified by setting (inpatient/outpatient) and code position for inpatient encounters. Test characteristics and 95% confidence intervals (CIs) were calculated using test-positive influenza as a reference standard. Test characteristics of alternative outpatient algorithms incorporating CPT/HCPCS testing codes and anti-influenza medication pharmacy claims were also calculated.

RESULTS

There were 430 documented influenza test results within the study period (295 inpatient, 135 outpatient). The claims-based influenza definition had a sensitivity of 84.9% (95% CI 72.9%-92.1%), specificity of 96.3% (95% CI 93.1%-98.0%), and PPV of 83.3% (95% CI 71.3%-91.0%) in the inpatient setting, and a sensitivity of 76.7% (95% CI 59.1%-88.2%), specificity of 96.2% (95% CI 90.6%-98.5%), PPV of 85.2% (95% CI 67.5%-94.1%) in the outpatient setting. Primary inpatient discharge diagnoses had a sensitivity of 54.7% (95% CI 41.5%-67.3%), specificity of 99.6% (95% CI 97.7%-99.9%), and PPV of 96.7% (95% CI 83.3%-99.4%). CPT/HCPCS codes and anti-influenza medication claims were present for few outpatient encounters (sensitivity 3%-10%).

CONCLUSIONS

In a large US healthcare system, inpatient ICD-10-CM codes for influenza, particularly primary inpatient diagnoses, had high predictive value for test-positive influenza. Outpatient ICD-10-CM codes were moderately predictive of test-positive influenza.

Concurrent Administration of COVID-19 and Influenza Vaccines Enhances Spike-Specific Antibody Responses

Background

The bivalent COVID-19 mRNA boosters became available in fall 2022 and were recommended alongside the seasonal influenza vaccine. However, the immunogenicity of concurrent vs separate administration of these vaccines remains unclear.

Methods

Here, we analyzed antibody responses in health care workers who received the bivalent COVID-19 booster and the influenza vaccine on the same day or on different days through systems serology. Antibody-binding and functional responses were characterized at peak responses and after 6 months following vaccination.

Results

IgG1 and neutralization responses to SARS-CoV-2 XBB.1.5 were higher at peak and after 6 months following concurrent administration as compared with separate administration of the COVID-19 and influenza vaccines. While similar results were not observed for influenza responses, no interference was noted with concurrent administration.

Conclusions

These data suggest that concurrent administration of these vaccines may yield higher and more durable SARS-CoV-2 neutralizing antibody responses while maintaining responses against influenza.

Divergent Pathogenesis and Transmission of Highly Pathogenic Avian Influenza A(H5N1) in Swine

Highly pathogenic avian influenza (HPAI) viruses have potential to cross species barriers and cause pandemics. Since 2022, HPAI A(H5N1) belonging to the goose/Guangdong 2.3.4.4b hemagglutinin phylogenetic clade have infected poultry, wild birds, and mammals across North America. Continued circulation in birds and infection of multiple mammalian species with strains possessing adaptation mutations increase the risk for infection and subsequent reassortment with influenza A viruses endemic in swine. We assessed the susceptibility of swine to avian and mammalian HPAI H5N1 clade 2.3.4.4b strains using a pathogenesis and transmission model. All strains replicated in the lung of pigs and caused lesions consistent with influenza A infection. However, viral replication in the nasal cavity and transmission was only observed with mammalian isolates. Mammalian adaptation and reassortment may increase the risk for incursion and transmission of HPAI viruses in feral, backyard, or commercial swine.

Coinfection of Influenza A and B and Human OC43 Coronavirus in Normal Human Bronchial Epithelial Cells

BACKGROUND

Influenza viruses and seasonal coronaviruses are pathogens transmitted via an airborne route that can cause respiratory diseases in humans that have similar symptoms such as fever, cough, and pneumonia. These two viruses can infect similar human tissues, such as the respiratory tract and nasal, bronchial, and alveolar epithelial cells. Influenza virus and seasonal coronavirus coinfections are poorly understood.

METHODS

Here, we coinfected normal human bronchial epithelial (NHBE) cells with influenza A/California/04/09 (IAV) or B/Victoria/504/2000 (IBV) strains and the seasonal human beta-coronavirus OC43 and evaluated viral replication capacities. We also examined changes in the expression of various cytokines/chemokines by qPCR and Luminex assay.

RESULTS

We observed that the replication of IAV and IBV was not affected by coinfection with OC43. However, coinfection reduced OC43 titers (~3-fold) compared with infection with OC43 alone. Select cytokine/chemokine expression was increased in coinfected cells compared with all single infections with greater differences seen between coinfected cells and cells infected with OC43 alone compared with IAV- or IBV-infected cells. In addition, IL-8 and IL-1RA showed the highest expression among a panel of 22 cytokines by Luminex.

CONCLUSIONS

As the rate of influenza and seasonal coronavirus coinfection continue to increase, our findings may help set guidelines for the treatments of the individuals coinfected with both viruses.

An Intense Out-of-Season Rebound of Influenza Activity After the Relaxation of Coronavirus Disease 2019 Restrictions in Beijing, China

Background

The aim of this study was to investigate the changes of epidemic characteristics of influenza activity pre- and post-coronavirus disease 2019 (COVID-19) in Beijing, China.

Methods

Epidemiologic data were collected from the influenza surveillance system in Beijing. We compared epidemic intensity, epidemic onset and duration, and influenza transmissibility during the 2022-2023 season with pre-COVID-19 seasons from 2014 to 2020.

Results

The overall incidence rate of influenza in the 2022-2023 season was significantly higher than that of the pre-COVID-19 period, with the record-high level of epidemic intensity in Beijing. The onset and duration of the influenza epidemic period in 2022-2023 season was notably later and shorter than that of the 2014-2020 seasons. Maximum daily instantaneous reproduction number (Rt) of the 2022-2023 season (Rt = 2.31) was much higher than that of the pre-COVID-19 period (Rt = 1.49). The incidence of influenza A(H1N1) and A(H3N2) were the highest among children aged 0-4 years and 5-14 years, respectively, in the 2022-2023 season.

Conclusions

A late, intense, and short-term peak influenza activity was observed in the 2022-2023 season in Beijing. Children <15 years old were impacted the most by the interruption of influenza circulation during the COVID-19 pandemic. Maintaining continuous surveillance and developing targeted public health strategies of influenza is necessary.

Evaluating Pilot Implementation of 'PenCS Flu Topbar' App in Medical Practices to Improve National Immunisation Program-Funded Seasonal Influenza Vaccination in Central Queensland, Australia

BACKGROUND

The 'PenCS Flu Topbar' app was deployed in Central Queensland (CQ), Australia, medical practices through a pilot programme in March 2021.

METHODS

We evaluated the app's user experience and examined whether the introduction of 'PenCS Flu Topbar' in medical practices could improve the coverage of NIP-funded influenza vaccinations. We conducted a mixed-method study including a qualitative analysis of in-depth interviews with key end-users and a quantitative analysis of influenza vaccine administrative data.

RESULTS

'PenCS Flu Topbar' app users reported positive experiences identifying patients eligible for NIP-funded seasonal influenza vaccination. A total of 3606 NIP-funded influenza vaccinations was administered in the eight intervention practices, 14% higher than the eight control practices. NIP-funded vaccination coverage within practices was significantly higher in the intervention practices (31.2%) than in the control practices (27.3%) (absolute difference: 3.9%; 95% CI: 2.9%-5.0%; p < 0.001). The coverage was substantially higher in Aboriginal and Torres Strait Islander people aged more than 6 months, pregnant women and children aged 6 months to less than 5 years for the practices where the app was introduced when compared to control practices: incidence rate ratio (IRR) 2.4 (95% CI: 1.8-3.2), IRR 2.7 (95% CI: 1.8-4.2) and IRR 2.3 (1.8-2.9) times higher, respectively.

CONCLUSIONS

Our evaluation indicated that the 'PenCS Flu Topbar' app is useful for identifying the patients eligible for NIP-funded influenza vaccination and is likely to increase NIP-funded influenza vaccine coverage in the eligible populations. Future impact evaluation including a greater number of practices and a wider geographical area is essential.

Clinical outcomes of baloxavir versus oseltamivir in immunocompromised patients

BACKGROUND

Neuraminidase inhibitors, including oseltamivir, are the treatment standard for influenza. Baloxavir, a novel antiviral, demonstrated comparable outcomes to oseltamivir in outpatients with influenza. Baloxavir was equally effective as oseltamivir in a retrospective study of hospitalized patients with influenza at our institution. However, the efficacy of baloxavir in immunocompromised patients is unclear.

METHODS

We conducted a retrospective cohort study of immunocompromised adult patients hospitalized with influenza A who received baloxavir from January 2019 to April 2019 or oseltamivir from January 2018 to April 2018. Demographic and clinical outcomes were assessed. Primary outcomes were time from antiviral initiation to resolution of hypoxia and fever. Secondary outcomes were length of stay (LOS), intensive care unit (ICU) care, ICU LOS, and 30-day mortality.

RESULTS

Of 95 total patients, 52 received baloxavir and 43 received oseltamivir. Other than younger age (57.5 vs. 65; p = .035) and longer duration between vaccination and symptom onset (114 vs. 86 days; p = .001) in the baloxavir group, baseline characteristics did not differ. H1 was the predominant subtype in the baloxavir group (65.3%) versus H3 in the oseltamivir group (85.7%). When comparing baloxavir to oseltamivir, there was no significant difference in median time from antiviral initiation to resolution of hypoxia (59.9 vs. 42.5 h) and to resolution of fever (21.6 vs. 26.6 h). There were no differences in secondary outcomes.

CONCLUSION

Baloxavir was not associated with longer time to resolution of hypoxia or fever in comparison to oseltamivir. Results must be taken in context of variations in seasonal influenza subtype and resistance rates.

Risk of stroke within 3, 7, 14, 21 and 30 days after influenza vaccination in Alberta, Canada: A population-based study

BACKGROUND AND PURPOSE

Influenza vaccination is associated with a longer-term protective effect against stroke; however, it has a short-term inflammatory response which may increase short-term risk of stroke. The aim was to investigate the association between influenza vaccination and short-term risk of stroke in adults.

METHODS

Administrative data were obtained from the Alberta Health Care Insurance Plan for all adults in Alberta, Canada, from September 2009 to December 2018. The hazard of any stroke (acute ischaemic stroke, intracerebral haemorrhage, subarachnoid haemorrhage and transient ischaemic attack) within 3, 7, 14, 21 and 30 days of influenza vaccination compared to unexposed time was analysed using Andersen-Gill Cox models, with adjustment for age, sex, anticoagulant use, atrial fibrillation, chronic obstructive pulmonary disease, diabetes, hypertension, income quintile, and rural or urban home location.

RESULTS

In the entire cohort consisting of 4,141,209 adults (29,687,899 person-years), 1,769,565 (42.7%) individuals received at least one vaccination. In total 38,126 stroke events were recorded with 1309 occurring within 30 days of a vaccination event. Influenza vaccination was associated with a significantly reduced hazard of stroke within 3 days (hazard ratio [HR] 0.83, 95% confidence interval [CI] 0.73-0.93), 7 days (HR 0.87, 95% CI 0.80-0.95), 14 days (HR 0.87, 95% CI 0.81-0.93), 21 days (HR 0.85, 95% CI 0.80-0.91) and 30 days (HR 0.66, 95% CI 0.65-0.68).

CONCLUSIONS

An increased early risk associated with vaccination was not observed. The risk of stroke was reduced at all time points within 30 days after influenza vaccination.

Seroprevalence of Avian Influenza A(H5N6) Virus Infection, Guangdong Province, China, 2022

In 2022, we assessed avian influenza A virus subtype H5N6 seroprevalence among the general population in Guangdong Province, China, amid rising numbers of human infections. Among the tested samples, we found 1 to be seropositive, suggesting that the virus poses a low but present risk to the general population.

Usefulness of a pluralistic approach in sentinel surveillance: seasonal influenza activity based on case counts per sentinel site in the National Epidemiological Surveillance of Infectious Diseases Program and test counts, case counts, and test positivity from the National Hospital Organization

In Japan, based on the National Epidemiological Surveillance of Infectious Diseases (NESID) Program, influenza cases from ~5,000 sentinel sites are monitored weekly as part of influenza surveillance (as number of influenza cases/sentinel site). One limitation is that the number of influenza tests conducted is not reported. Separately, the National Hospital Organization (NHO), with ~140 hospitals, routinely publishes three indicators: number of influenza tests, influenza-positive case counts, and test positivity. We used NESID and NHO data from April 2011 to June 2022 to assess the usefulness of multiple indicators to monitor influenza activity. Temporal trends of the NHO and NESID indicators were similar, and NHO indicator levels well-correlated with those of the NESID indicator. Influenza positivity in the NHO data, however, showed an earlier rise and peak time compared to the NESID indicator. Importantly, through the non-epidemic summer periods and the coronavirus disease 2019 pandemic, a sizable number of influenza tests continued to be done at NHO hospitals, with results showing considerably low case counts and test positivity. These data show that a relatively small number of sentinel sites is sufficient to monitor influenza activity nationally, and, that utilizing multiple indicators can increase our confidence in situational awareness and data interpretations.

Bioinformatics and system biology approach to identify the influences among COVID-19, influenza, and HIV on the regulation of gene expression

Background

Coronavirus disease (COVID-19), caused by SARS-CoV-2, has emerged as a infectious disease, coexisting with widespread seasonal and sporadic influenza epidemics globally. Individuals living with HIV, characterized by compromised immune systems, face an elevated risk of severe outcomes and increased mortality when affected by COVID-19. Despite this connection, the molecular intricacies linking COVID-19, influenza, and HIV remain unclear. Our research endeavors to elucidate the shared pathways and molecular markers in individuals with HIV concurrently infected with COVID-19 and influenza. Furthermore, we aim to identify potential medications that may prove beneficial in managing these three interconnected illnesses.

Methods

Sequencing data for COVID-19 (GSE157103), influenza (GSE185576), and HIV (GSE195434) were retrieved from the GEO database. Commonly expressed differentially expressed genes (DEGs) were identified across the three datasets, followed by immune infiltration analysis and diagnostic ROC analysis on the DEGs. Functional enrichment analysis was performed using GO/KEGG and Gene Set Enrichment Analysis (GSEA). Hub genes were screened through a Protein-Protein Interaction networks (PPIs) analysis among DEGs. Analysis of miRNAs, transcription factors, drug chemicals, diseases, and RNA-binding proteins was conducted based on the identified hub genes. Finally, quantitative PCR (qPCR) expression verification was undertaken for selected hub genes.

Results

The analysis of the three datasets revealed a total of 22 shared DEGs, with the majority exhibiting an area under the curve value exceeding 0.7. Functional enrichment analysis with GO/KEGG and GSEA primarily highlighted signaling pathways associated with ribosomes and tumors. The ten identified hub genes included IFI44L, IFI44, RSAD2, ISG15, IFIT3, OAS1, EIF2AK2, IFI27, OASL, and EPSTI1. Additionally, five crucial miRNAs (hsa-miR-8060, hsa-miR-6890-5p, hsa-miR-5003-3p, hsa-miR-6893-3p, and hsa-miR-6069), five essential transcription factors (CREB1, CEBPB, EGR1, EP300, and IRF1), and the top ten significant drug chemicals (estradiol, progesterone, tretinoin, calcitriol, fluorouracil, methotrexate, lipopolysaccharide, valproic acid, silicon dioxide, cyclosporine) were identified.

Conclusion

This research provides valuable insights into shared molecular targets, signaling pathways, drug chemicals, and potential biomarkers for individuals facing the complex intersection of COVID-19, influenza, and HIV. These findings hold promise for enhancing the precision of diagnosis and treatment for individuals with HIV co-infected with COVID-19 and influenza.

Use of Sentinel Surveillance Platforms for Monitoring SARS-CoV-2 Activity: Evidence From Analysis of Kenya Influenza Sentinel Surveillance Data

BACKGROUND

Little is known about the cocirculation of influenza and SARS-CoV-2 viruses during the COVID-19 pandemic and the use of respiratory disease sentinel surveillance platforms for monitoring SARS-CoV-2 activity in sub-Saharan Africa.

OBJECTIVE

We aimed to describe influenza and SARS-CoV-2 cocirculation in Kenya and how the SARS-CoV-2 data from influenza sentinel surveillance correlated with that of universal national surveillance.

METHODS

From April 2020 to March 2022, we enrolled 7349 patients with severe acute respiratory illness or influenza-like illness at 8 sentinel influenza surveillance sites in Kenya and collected demographic, clinical, underlying medical condition, vaccination, and exposure information, as well as respiratory specimens, from them. Respiratory specimens were tested for influenza and SARS-CoV-2 by real-time reverse transcription polymerase chain reaction. The universal national-level SARS-CoV-2 data were also obtained from the Kenya Ministry of Health. The universal national-level SARS-CoV-2 data were collected from all health facilities nationally, border entry points, and contact tracing in Kenya. Epidemic curves and Pearson r were used to describe the correlation between SARS-CoV-2 positivity in data from the 8 influenza sentinel sites in Kenya and that of the universal national SARS-CoV-2 surveillance data. A logistic regression model was used to assess the association between influenza and SARS-CoV-2 coinfection with severe clinical illness. We defined severe clinical illness as any of oxygen saturation <90%, in-hospital death, admission to intensive care unit or high dependence unit, mechanical ventilation, or a report of any danger sign (ie, inability to drink or eat, severe vomiting, grunting, stridor, or unconsciousness in children younger than 5 years) among patients with severe acute respiratory illness.

RESULTS

Of the 7349 patients from the influenza sentinel surveillance sites, 76.3% (n=5606) were younger than 5 years. We detected any influenza (A or B) in 8.7% (629/7224), SARS-CoV-2 in 10.7% (768/7199), and coinfection in 0.9% (63/7165) of samples tested. Although the number of samples tested for SARS-CoV-2 from the sentinel surveillance was only 0.2% (60 per week vs 36,000 per week) of the number tested in the universal national surveillance, SARS-CoV-2 positivity in the sentinel surveillance data significantly correlated with that of the universal national surveillance (Pearson r=0.58; P<.001). The adjusted odds ratios (aOR) of clinical severe illness among participants with coinfection were similar to those of patients with influenza only (aOR 0.91, 95% CI 0.47-1.79) and SARS-CoV-2 only (aOR 0.92, 95% CI 0.47-1.82).

CONCLUSIONS

Influenza substantially cocirculated with SARS-CoV-2 in Kenya. We found a significant correlation of SARS-CoV-2 positivity in the data from 8 influenza sentinel surveillance sites with that of the universal national SARS-CoV-2 surveillance data. Our findings indicate that the influenza sentinel surveillance system can be used as a sustainable platform for monitoring respiratory pathogens of pandemic potential or public health importance.

Clinical Evaluation of Xpert Xpress CoV-2/Flu/RSV plus and Alinity m Resp-4-Plex Assay

The performance of the Xpert Xpress CoV-2/Flu/RSV plus and Alinity m Resp-4-Plex Assays were evaluated using 167 specimens, including 158 human respiratory specimens and 9 external quality assessment program (EQAP) samples. For respiratory specimens, CoV-2/Flu/RSV plus exhibited perfect agreement with the standard-of-care (SOC) methods (Cohen's κ: 1, 100% agreement). The overall positive and negative percent agreement (PPA and NPA) were 100%, with 95% confidence intervals of 96.50 to 100% and 85.70 to 100%, respectively. On the other hand, Resp-4-Plex revealed an almost perfect agreement with the SOC methods (Cohen's κ: 0.92, 97.71% agreement). The overall PPA and NPA were 100% (95.76 to 100%) and 88.46% (70.20 to 96.82%), respectively. For EQAP samples, the results of CoV-2/Flu/RSV plus (9/9) and Resp-4-Plex (4/4) were concordant with the expected results. The experimental limit of detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the lowest (25 copies/mL for both methods), and that of the respiratory syncytial virus was the highest (400 copies/mL for CoV-2/Flu/RSV plus and 100 copies/mL for Resp-4-Plex). Threshold cycle (Ct) value correlation showed a large positive linear association between CoV-2/Flu/RSV plus and Resp-4-Plex, with R-squared values of 0.92-0.97, and on average, the Ct values of CoV-2/Flu/RSV plus were higher than that of Resp-4-Plex by 1.86-2.78, except for Flu A1 target (-0.66). To conclude, the performance of both assay was comparable to the SOC methods for both upper and lower respiratory specimens. Implementation of these rapid assay may reinforce the diagnostic capacity for the post-pandemic co-circulation of SARS-CoV-2 and other respiratory viruses.

Impact of obstructive sleep apnea on clinical outcomes of hospitalization due to influenza in children: A propensity score-matched analysis of the US Nationwide Inpatient Sample 2005-2018

BACKGROUND

Previous studies have explored the association between obstructive sleep apnea (OSA) and clinical outcomes of influenza in adults, whereas limited research examined this relationship in pediatric populations. This study aimed to evaluate the clinical impact of OSA on the outcomes of pediatric influenza hospitalizations.

METHODS

This was a population-based, retrospective study. Data of children aged 1-19 years hospitalized for influenza infection were extracted from the United States (US) Nationwide Inpatient Sample Database 2005-2018. Univariable and multivariable regression analyses determined associations between OSA, length of stay (LOS), total hospital costs, pneumonia, and life-threatening events.

RESULTS

After propensity-score matching, a total of 2100 children were analyzed. The logistic analysis revealed that children with OSA had a significantly increased LOS (β = 2.29 days; 95% confidence interval, CI: 1.01-3.57, p < .001) and total hospital costs (β = 26.06 thousand dollars; 95% CI: 6.62-45.51, p = .009), and higher odds of pneumonia (aged 6-10 years: odds ratio [OR] = 1.52; 95% CI: 1.01-2.27, p = .043; aged ≥ 11 years: OR = 1.83; 95% CI: 1.33-2.53, p < .001).

CONCLUSIONS

During influenza admissions, children with OSA had longer LOS, higher hospital costs, and an increased risk of pneumonia compared to those without OSA. These findings underscore the importance of recognizing and managing OSA in influenza-related infections among children.

Influenza Hospitalization Burden by Subtype, Age, Comorbidity, and Vaccination Status: 2012-2013 to 2018-2019 Seasons, Quebec, Canada

BACKGROUND

Influenza immunization programs aim to reduce the risk and burden of severe outcomes. To inform optimal program strategies, we monitored influenza hospitalizations over 7 seasons, stratified by age, comorbidity, and vaccination status.

METHODS

We assembled data from 4 hospitals involved in an active surveillance network with systematic collection of nasal samples and polymerase chain reaction testing for influenza virus in all patients admitted through the emergency department with acute respiratory infection during the 2012-2013 to 2018-2019 influenza seasons in Quebec, Canada. We estimated seasonal, population-based incidence of influenza-associated hospitalizations by subtype predominance, age, comorbidity, and vaccine status, and derived the number needed to vaccinate to prevent 1 hospitalization per stratum.

RESULTS

The average seasonal incidence of influenza-associated hospitalization was 89/100 000 (95% confidence interval, 86-93), lower during A(H1N1) (49-82/100 000) than A(H3N2) seasons (73-143/100 000). Overall risk followed a J-shaped age pattern, highest among infants 0-5 months and adults ≥75 years old. Hospitalization risks were highest for children <5 years old during A(H1N1) but for highest adults aged ≥75 years during A(H3N2) seasons. Age-adjusted hospitalization risks were 7-fold higher among individuals with versus without comorbid conditions (214 vs 30/100 000, respectively). The number needed to vaccinate to prevent hospitalization was 82-fold lower for ≥75-years-olds with comorbid conditions (n = 1995), who comprised 39% of all hospitalizations, than for healthy 18-64-year-olds (n = 163 488), who comprised just 6% of all hospitalizations.

CONCLUSIONS

In the context of broad-based influenza immunization programs (targeted or universal), severe outcome risks should be simultaneously examined by subtype, age, comorbidity, and vaccine status. Policymakers require such detail to prioritize promotional efforts and expenditures toward the greatest and most efficient program impact.

Vaccine Effectiveness Against Pediatric Influenza-A-Associated Urgent Care, Emergency Department, and Hospital Encounters During the 2022-2023 Season: VISION Network

BACKGROUND

During the 2022-2023 influenza season, the United States experienced the highest influenza-associated pediatric hospitalization rate since 2010-2011. Influenza A/H3N2 infections were predominant.

METHODS

We analyzed acute respiratory illness (ARI)-associated emergency department or urgent care (ED/UC) encounters or hospitalizations at 3 health systems among children and adolescents aged 6 months-17 years who had influenza molecular testing during October 2022-March 2023. We estimated influenza A vaccine effectiveness (VE) using a test-negative approach. The odds of vaccination among influenza-A-positive cases and influenza-negative controls were compared after adjusting for confounders and applying inverse-propensity-to-be-vaccinated weights. We developed overall and age-stratified VE models.

RESULTS

Overall, 13 547 of 44 787 (30.2%) eligible ED/UC encounters and 263 of 1862 (14.1%) hospitalizations were influenza-A-positive cases. Among ED/UC patients, 15.2% of influenza-positive versus 27.1% of influenza-negative patients were vaccinated; VE was 48% (95% confidence interval [CI], 44-52%) overall, 53% (95% CI, 47-58%) among children aged 6 months-4 years, and 38% (95% CI, 30-45%) among those aged 9-17 years. Among hospitalizations, 17.5% of influenza-positive versus 33.4% of influenza-negative patients were vaccinated; VE was 40% (95% CI, 6-61%) overall, 56% (95% CI, 23-75%) among children ages 6 months-4 years, and 46% (95% CI, 2-70%) among those 5-17 years.

CONCLUSIONS

During the 2022-2023 influenza season, vaccination reduced the risk of influenza-associated ED/UC encounters and hospitalizations by almost half (overall VE, 40-48%). Influenza vaccination is a critical tool to prevent moderate-to-severe influenza illness in children and adolescents.

Integrating single-cell RNA sequencing data to genome-wide association analysis data identifies significant cell types in influenza A virus infection and COVID-19

With the global pandemic of COVID-19, the research on influenza virus has entered a new stage, but it is difficult to elucidate the pathogenesis of influenza disease. Genome-wide association studies (GWASs) have greatly shed light on the role of host genetic background in influenza pathogenesis and prognosis, whereas single-cell RNA sequencing (scRNA-seq) has enabled unprecedented resolution of cellular diversity and in vivo following influenza disease. Here, we performed a comprehensive analysis of influenza GWAS and scRNA-seq data to reveal cell types associated with influenza disease and provide clues to understanding pathogenesis. We downloaded two GWAS summary data, two scRNA-seq data on influenza disease. After defining cell types for each scRNA-seq data, we used RolyPoly and LDSC-cts to integrate GWAS and scRNA-seq. Furthermore, we analyzed scRNA-seq data from the peripheral blood mononuclear cells (PBMCs) of a healthy population to validate and compare our results. After processing the scRNA-seq data, we obtained approximately 70 000 cells and identified up to 13 cell types. For the European population analysis, we determined an association between neutrophils and influenza disease. For the East Asian population analysis, we identified an association between monocytes and influenza disease. In addition, we also identified monocytes as a significantly related cell type in a dataset of healthy human PBMCs. In this comprehensive analysis, we identified neutrophils and monocytes as influenza disease-associated cell types. More attention and validation should be given in future studies.

Two complete 1918 influenza A/H1N1 pandemic virus genomes characterized by next-generation sequencing using RNA isolated from formalin-fixed, paraffin-embedded autopsy lung tissue samples along with evidence of secondary bacterial co-infection

The 1918 influenza pandemic was the most devastating respiratory pandemic in modern human history, with 50-100 million deaths worldwide. Here, we characterized the complete genomes of influenza A virus (IAV) from two fatal cases during the fall wave of 1918 influenza A (H1N1) pandemic in the United States, one from Walter Reed Army Hospital in Washington, DC, and the other from Camp Jackson, SC. The two complete IAV genomes were obtained by combining Illumina deep sequencing data from both total RNA and influenza viral genome-enriched libraries along with Sanger sequencing data from PCR across the sequencing gaps. This study confirms the previously reported 1918 IAV genomes and increases the total number of available complete or near-complete influenza viral genomes of the 1918 pandemic from four to six. Sequence comparisons among them confirm that the genomes of the 1918 pandemic virus were highly conserved during the main wave of the pandemic with geographic separation in North America and Europe. Metagenomic analyses revealed bacterial co-infections in both cases. Interestingly, in the Washington, DC, case, evidence is presented of the first reported Rhodococcus-influenza virus co-infection.

IMPORTANCE

This study applied modern molecular biotechnology and high-throughput sequencing to formalin-fixed, paraffin-embedded autopsy lung samples from two fatal cases during the fall wave of the 1918 influenza A (H1N1) pandemic in the United States. Complete influenza genomes were obtained from both cases, which increases the total number of available complete or near-complete influenza genomes of the 1918 pandemic virus from four to six. Sequence analysis confirms that the 1918 pandemic virus was highly conserved during the main wave of the pandemic with geographic separation in North America and Europe. Metagenomic analyses revealed bacterial co-infections in both cases, including the first reported evidence of Rhodococcus-influenza co-infection. Overall, this study offers a detailed view at the molecular level of the very limited samples from the most devastating influenza pandemic in modern human history.

Influenza: cause or excuse? An analysis of flu's influence on worsening mortality trends in England and Wales, 2010-19

BACKGROUND

England and Wales experienced a stagnation of previously improving life expectancy during the 2010s. Public bodies cited influenza as an important cause.

SOURCES OF DATA

We used data from the Office for National Statistics to examine mortality attributed directly to influenza and to all influenza-like diseases for the total population of England and Wales 2010-19. Several combinations of ICD-10 codes were used to address the possibility of under-counting influenza deaths.

AREAS OF AGREEMENT

Deaths from influenza and influenza-like diseases declined between 2010 and 2019, while earlier improvements in mortality from all causes of death were stalling and, with some causes, worsening. Our findings support existing research showing that influenza is not an important cause of the stalling of mortality rates 2010-19.

AREAS OF CONTROVERSY

Influenza was accepted by many as an important cause of stalling life expectancy for much of the 2010s, while few in public office have accepted austerity as a key factor in the changes seen during that time.

GROWING POINTS

This adds to the mounting evidence that austerity damaged health prior to COVID-19 and left the population more vulnerable when it arrived.

AREAS FOR DEVELOPING TIMELY RESEARCH

Future research should explore why so many in public office were quick to attribute the change in trends in overall mortality in the UK in this period to influenza, and why many continue to do so through to 2023 and to deny the key role of austerity in harming population health.

Intestinal microbiota programming of alveolar macrophages influences severity of respiratory viral infection

Susceptibility to respiratory virus infections (RVIs) varies widely across individuals. Because the gut microbiome impacts immune function, we investigated the influence of intestinal microbiota composition on RVI and determined that segmented filamentous bacteria (SFB), naturally acquired or exogenously administered, protected mice against influenza virus (IAV) infection. Such protection, which also applied to respiratory syncytial virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was independent of interferon and adaptive immunity but required basally resident alveolar macrophages (AMs). In SFB-negative mice, AMs were quickly depleted as RVI progressed. In contrast, AMs from SFB-colonized mice were intrinsically altered to resist IAV-induced depletion and inflammatory signaling. Yet, AMs from SFB-colonized mice were not quiescent. Rather, they directly disabled IAV via enhanced complement production and phagocytosis. Accordingly, transfer of SFB-transformed AMs into SFB-free hosts recapitulated SFB-mediated protection against IAV. These findings uncover complex interactions that mechanistically link the intestinal microbiota with AM functionality and RVI severity.