Search Results (613)

Introduction: While influenza-associated encephalopathy (IAE) in children remains a serious concern, recent evidence suggests a shift in its epidemiology, with a possible decline in incidence and severity over time. Methods: This retrospective review includes patients aged 0–18 admitted to a tertiary hospital in Northern Italy between November 2023 and February 2025. Inclusion criteria were a positive influenza test, influenza-like symptoms, and neurological involvement. Findings are interpreted alongside current literature. Results: Twenty-five unvaccinated children met criteria for IAE (11 in 2023/24; 14 in 2024/25). Neurological comorbidities were present in 40%. All patients had pathological EEGs. Lumbar puncture was performed in 40%, with abnormalities in 33%. Brain imaging was conducted in 56% of cases, revealing findings in 15%. All received oseltamivir; 60% were also treated with dexamethasone. Severe complications occurred in 16%, while 12% had persistent symptoms or required therapy at discharge. After adjusting for seasonal peak timing, no significant inter-seasonal difference was observed. Discussion: Although IAE continues to present serious risks, recent trends suggest a changing burden. The lack of vaccination among cases underscores the need for prevention. Study limitations include its single-center design and the absence of long-term follow-up. Broader prospective studies are needed. Full article

The SARS-CoV-2 pandemic and the implementation of associated non-pharmaceutical interventions (NPIs) profoundly altered the epidemiology of seasonal influenza viruses. To investigate these changes, we analyzed influenza-like illness samples in Shenzhen, China, across six influenza seasons spanning 2018 to 2024. Influenza activity declined markedly during the SARS-CoV-2 pandemic compared with the pre-pandemic period but returned to or even exceeded pre-pandemic levels in the post-pandemic era. Phylogenetic analysis of hemagglutinin (HA) and neuraminidase (NA) genes from 58 H1N1pdm09, 78 H3N2, and 97 B/Victoria isolates revealed substantial genetic divergence from the WHO-recommended vaccine strains. Notably, key mutations in the HA genes of H1N1pdm09, H3N2, and B/Victoria viruses were concentrated in the receptor-binding site (RBS) and adjacent antigenic sites. Hemagglutination inhibition (HI) assays demonstrated that most circulating viruses remained antigenically matched to their corresponding vaccine strains. However, significant antigenic drift was observed in H3N2 clade 3C.2a1b.1b viruses during the 2018–2019 season and in B/Victoria clade V1A.3a.2 viruses during the 2023–2024 season. These findings highlight the impact of NPIs and pandemic-related disruptions on influenza virus circulation and evolution, providing critical insights for future surveillance and public health preparedness. Full article

Background: Influenza is an acute viral disease that primarily affects the airways. It is caused by influenza A and B—RNA viruses. The disease is associated with significant morbidity and mortality. The prevention of influenza includes chemoprophylaxis and vaccination, which are the primary preventive measures against influenza infection and should be highly considered by everyone during influenza season. Methods: A systematic literature search was performed in the databases of PubMed, Web of Science, Scopus, and Embase until September 2024. The review was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. Results: Eventually, a total of 20 publications were included in the final analysis of this systematic review. While general awareness of influenza was moderate, detailed understanding of complications and vaccine safety was frequently lacking. Misconceptions—such as fears of fetal harm and confusion between antiviral and antibiotic treatments—were widespread. Vaccine uptake was generally low but strongly correlated with receiving a healthcare provider recommendation. Willingness to vaccinate was higher in settings where participants were educated during the study process, indicating a crucial role of health communication. Discussion: According to the reviewed literature, the reluctance to receive maternal vaccination often stems primarily from fears or concerns about adverse reactions or misconceptions about the vaccine’s effectiveness, as well as the absence of a physician’s recommendation. Misconceptions regarding vaccine safety, limited understanding of influenza severity, and a lack of clear communication from healthcare professionals are key contributors to low vaccination uptake. Importantly, multiple studies confirmed that recommendation by a trusted healthcare provider significantly increases vaccine acceptance. Conclusions: These findings highlight the urgent need for targeted educational strategies, improved antenatal counseling, and systems-level support to ensure that maternal influenza vaccination becomes a standard and trusted component of prenatal care worldwide. Full article

Background/Objectives: Seasonal influenza vaccination is crucial for reducing morbidity, mortality, and healthcare burdens. The 2023/2024 Ligurian vaccination campaign (Italy) utilized an inclusive model involving local health authorities, general practitioners, pediatricians, and pharmacies to enhance accessibility. Our study aimed at focusing on factors influencing vaccine uptake, public attitudes and access to preventive healthcare services. Methods: A cross-sectional survey was conducted among adults (≥18 years) in Ligurian pharmacies visitors during the vaccination campaign. A self-administered structured questionnaire gathered data on demographics, vaccination history, healthcare access, and awareness. Results: The study included 30,499 participants, and the median age with P25–P75 (years) was 62.0 [47.0–74.0]; 54.6% were female. Considering determinants of accepting influenza vaccination, age was identified as a strong independent predictor. Each one-year increase in age was associated with a 3.8% increase in the odds of influenza vaccination (OR 1.03, 95% CI 1.03–1.04, p < 0.001). Compared to individuals who never visited their general practitioners, those who visited “sometimes”, “often”, or “very often” had significantly higher odds of influenza vaccination (OR 1.54, 1.97, and 1.98, respectively; p < 0.001 for all categories). The strongest predictor of influenza vaccination in the 2023/2024 season was having received the influenza vaccine in the previous season (2022/2023) (OR 71.73, 95% CI 65.38–78.78, p < 0.001). Consistent with increasing age predicting higher influenza vaccination uptake, older age was associated with lower odds of refusing the vaccine due to the belief that “getting or transmitting influenza does not matter” or due to “other or unspecified reasons”. In contrast, receipt of the COVID-19 vaccination significantly increased the odds of holding these opinions. Among individuals who cited reasons such as fear of side effects, concerns about vaccine safety, fear of injections, general opposition to vaccines, or doubts about vaccine effectiveness, having received the COVID-19 vaccine was associated with lower odds of citing these as barriers to influenza vaccination. Conclusions: Fear of side effects and perceived unnecessary vaccination are key barriers. Targeted education and the involvement of general practitioners could enhance vaccine acceptance, particularly among hesitant groups. Full article

Background/Objectives: The combination of a hemagglutinin antigen (HA)-based inactivated influenza vaccine (IIV; Fluarix^® Tetra; GlaxoSmithKline) with a nucleoprotein (NP)-based vaccine, such as OVX836, should increase the efficacy of influenza vaccines since it leverages two complementary immunological mechanisms: HA antibodies targeting the virus envelope and neutralizing it, and an NP cell-mediated immune (CMI) response destroying infected cells. Methods: This was a randomized, double-blind, Phase 2a study (ClinicalTrials.gov NCT05284799) including three groups of 60 healthy subjects (18–55 years old) receiving either IIV + placebo, IIV + OVX836 (480 µg), or OVX836 + placebo intramuscularly and concomitantly into the same deltoid muscle. The endpoints were reactogenicity, safety, and immunogenicity (hemagglutination inhibition assay [HAI], anti-NP immunoglobulin G [IgG], and NP-specific cell-mediated immunity [CMI]). Results: The co-administration of IIV + OVX836 was safe and well-tolerated. The HAI response was strong and similar in the two IIV groups with no interference of OVX836. The humoral anti-NP IgG and NP-specific CMI responses to OVX836 were strong in the two OVX836 groups, and no major interference of IIV was observed. Conclusions: This study supports further clinical development of OVX836 as a combined IIV/OVX836 seasonal vaccine capable of inducing robust and complementary HAI and CMI NP-specific responses. Full article

This study proposes and examines the dynamics of a susceptible–exposed–infectious–recovered (SEIR) model for the spread of seasonal influenza. The population is categorized into four distinct groups: susceptible (S), exposed (E), infectious (I), and recovered (R) individuals. The symmetric model integrates a bilinear incidence rate alongside a nonlinear recovery rate that depends on the quality of healthcare services. Additionally, it accounts for the impact of fear related to the disease and includes a constant vaccination rate as well as a nonlinear treatment function. The model advances current epidemiological frameworks by simultaneously accounting for these interrelated mechanisms, which are typically studied in isolation. We derive the expression for the basic reproduction number and analyze the essential stability properties of the model. Key analytical results demonstrate that the system exhibits rich dynamic behavior, including backward bifurcation (where stable endemic equilibria persist even when the basic reproduction number is less than one) and Hopf bifurcation. These phenomena emerge from the interplay between fear-induced suppression of transmission, treatment saturation, and healthcare quality. Numerical simulations using Saudi Arabian demographic and epidemiological data quantify how increased fear perception shrinks the bistability region, facilitating eradication. Healthcare capacity improvements, on the other hand, reduce the critical reproduction number threshold while treatment accessibility suppresses infection loads. The model’s practical significance lies in its ability to identify intervention points where small parameter changes yield disproportionate control benefits and evaluate trade-offs between pharmaceutical (vaccination/treatment) and non-pharmaceutical (fear-driven distancing) strategies. This work establishes a versatile framework for public health decision making and the integrated approach offers policymakers a tool to simulate combined intervention scenarios and anticipate nonlinear system responses that simpler models cannot capture. Full article

Background/objectives: Influenza vaccines are recommended and free in Australia for children aged <5 years, but uptake remains low at 25.8% compared to the targets of 40% and 50%. National data on barriers hindering paediatric influenza vaccination can inform strategies to improve uptake. The aim of this study was to measure barriers to influenza vaccination in Australian children aged <5 years. Methods: A national, cross-sectional survey of parents of children aged <5 years was conducted in March/April 2024. Parents were recruited using an online panel and asked about their intention to get an influenza vaccine for their youngest child in the upcoming influenza season. An adapted version of the validated Vaccine Barriers Assessment Tool measured 14 influenza vaccination barriers. Analysis assessed the prevalence of barriers and differences between parents intending to and those unsure or not intending to vaccinate by calculating the prevalence difference and 95% confidence interval. Results: A total of 2000 parents were recruited nationally. The most common barrier was parents feeling distressed when thinking about vaccinating their child against influenza (66.1% of intending parents, 65.6% of unsure/not intending parents). The barrier with the largest difference between intending and not intending/unsure parents was not prioritising their child’s influenza vaccination (47.2% vs. 6.1%, PD = 41.1 ppts, 95% CI: 35.9%, 46.3%). Other barriers with large differences were parents not feeling guilty if their unvaccinated child got influenza (41.5% vs. 7.5%, PD = 34.0 ppts, 95% CI: 28.8%, 39.1%) and parents not believing that influenza vaccines are effective (31.3% vs. 3.0%, PD = 28.2 ppts, 95% CI: 23.6%, 32.9%). Conclusions: Parents should be encouraged and supported to prioritise influenza vaccination alongside routine childhood vaccines in campaigns that emphasise disease risk and the importance, safety and effectiveness of influenza vaccination, and by optimising access to influenza vaccination. We recommend conducting similar surveys regularly to monitor trends in parental barriers to childhood influenza vaccination. Full article

Influenza B, a globally prevalent respiratory virus, particularly affects children, the elderly, and individuals with chronic diseases. This retrospective single-center study analyzed long-term epidemiological trends using 23,284 PCR test results from Dankook University Hospital, Cheonan-si, Republic of Korea, from 2007 to 2024. The data included inpatients and outpatients who presented with respiratory symptoms and underwent multiplex PCR testing. Unlike previous studies focusing on short-term outbreaks, this study examines extended trends and emerging seasonal patterns. Positivity rates were statistically analyzed by year, season, sex, age group, and the impact of COVID-19 (2020–2022). Significant annual differences (p < 0.001) occurred, with peaks in 2012 and 2018 and a sharp decline during 2020–2022. Children exhibited the highest positivity rate (2.40%), significantly higher than that of adults (2.24%) and the elderly (1.79%) (p < 0.05). Infections peaked in the winter (2.98%) and spring (3.95%), contrary to the belief that Influenza B peaks in winter only. Females had a higher positivity rate (2.13%) than males (1.70%) (p = 0.017). These findings provide novel insights into Influenza B epidemiology, emphasizing the need for prevention strategies beyond winter. The secondary spring peak suggests extending vaccination to early spring may improve influenza control, particularly among high-risk groups. Full article

Background/Objectives: The co-circulation of both influenza viruses and SARS-CoV-2 poses a significant health risk, especially for the elderly. While vaccination against both diseases remains an effective strategy to reduce the burden of symptomatic infections, the effect of administering COVID-19 mRNA and seasonal influenza vaccines (COV-Flu) on elicited antibody responses has not been explored. Methods: Participants between 18 and 90 years old were vaccinated with COVID-19 mRNA vaccines (n = 67), seasonal influenza vaccines (n = 130), or both (n = 201) within a three-month period between 2021 and 2024. Serum hemagglutination-inhibition (HAI) titers against influenza A (H1N1, H3N2) and B (Yamagata, Victoria) strains were measured from the COV-Flu participants or the participants vaccinated with influenza vaccines only (mono-Flu). SARS-CoV-2 neutralization assays were performed on sera collected from the COV-Flu participants and the participants receiving the mRNA vaccine only (mono-COVID-19). Results: The administration of influenza virus vaccines and COVID-19 mRNA vaccines within a three-month period significantly enhanced the post-vaccination HAI titers against both influenza A and B vaccine components, particularly in the elderly (65–90) participants. There were no significant differences in SARS-CoV-2 neutralization titers in COV-Flu participants compared to mono-COVID-19 participants. Conclusions: Vaccination with both the COVID-19 mRNA and influenza vaccines enhances influenza-specific HAI titers without compromising the neutralization titers elicited by COVID-19 mRNA vaccination against SARS-CoV-2, especially in the elderly. These findings indicate the potential benefits of this approach, particularly for older adults, by boosting influenza virus vaccine-induced serum HAI activity while maintaining COVID-19 protective immunity. Full article

Background: Seasonal influenza viruses are primarily known for causing respiratory illness, but rare hematologic complications can occur, especially in young children. While influenza A is more commonly linked to severe manifestations, influenza B can similarly precipitate life-threatening cytopenias, particularly in toddlers. Case Presentation: We report the case of a previously healthy 1-year-and-8-months-old girl who presented with a high fever, cough, and marked pallor during peak influenza season. Laboratory tests revealed significant microcytic, hypochromic anemia and severe thrombocytopenia. Rapid antigen testing was positive for influenza B. An extensive workup for other causes of bicytopenia, including leukemia, hemolysis, aplastic anemia, and other viral infections, yielded negative results. The child was managed with urgent red blood cell and platelet transfusions, oseltamivir antiviral therapy, broad-spectrum antibiotics, corticosteroids, and supportive care. Bone marrow aspiration was deferred in light of the rapid hematologic recovery. Her hemoglobin greatly improved, and her platelet count reached normal values at discharge. Conclusions: Our case underscores the need to consider influenza in the differential diagnosis of unexplained cytopenias during flu season. This case illustrates that influenza B can mimic hematologic malignancies. Rapid diagnosis and supportive treatment are essential to avoid fatal outcomes. Influenza vaccination plays a significant role in preventing severe complications, such as those we encountered. Full article

Background: This study was aimed at understanding the attitude on influenza and influenza vaccination among workers of community healthcare centers (CHCs) and investigating the barriers and facilitators for influenza vaccination. Methods: A cross-sectional study was conducted through an anonymous questionnaire to all workers of CHCs in 22 CHCs. Socio-demographic characteristics, reasons for acceptance or refusal of influenza vaccination, influenza vaccination status, and attitude toward influenza vaccination were collected. Suggested strategies for improving influenza vaccine uptake were also surveyed. Descriptive analyses were conducted depending on the distributions of variables. A logistic regression analysis was implemented to examine the association between influenza vaccination status in the 2022/2023 season and the potential predictors. The adjusted odds ratio (AOR) with 95% confidence interval (CI) was calculated. Results: In total, 2205 workers of CHCs participated in this study. Influenza vaccination coverage in the 2022/2023 season was 1.36%. The reason “To avoid influenza” met with the highest level of agreement for acceptance of influenza vaccination (median = 4.36 for 1–5-point Likert scale), while the reason “Not a high-risk group of influenza and possible complications” met with the highest level of agreement for refusal of influenza vaccination (median = 3.72 for 1–5-point Likert scale). The influenza vaccination status was significantly related to professional categories, regular exercise habits, sources of information on influenza vaccination, and attitude on recommending influenza vaccination to patients. The free influenza vaccination and mandatory vaccination policies were the most frequent suggestions for improving influenza vaccination coverage. Conclusions: A lower influenza vaccination coverage was observed in workers of CHCs, and it might be attributed to several risk factors. It was urgent to take actions on improving their understanding of, awareness of, and confidence in influenza vaccination. Free influenza vaccination and vaccination requirement policies might be helpful for enhancing vaccine uptake, especially for physicians and other healthcare workers. Full article

Influenza (flu) is a highly prevalent respiratory illness caused by influenza viruses, representing a significant global health burden due to its substantial morbidity and mortality rate. Vaccination remains the most effective strategy for influenza prevention, and well-characterized animal models of influenza infection serve as essential tools for evaluating vaccine protective efficacy. However, animal models utilizing live influenza virus strains pose significant biosafety concerns, and many such strains are not readily available for research. To address these challenges, we established a novel visual mouse infection model using an HIV-based vector system. This model employs influenza pseudoviruses carrying a luciferase reporter gene, enabling real-time monitoring of viral load and in vivo tracking of viral distribution during infection. Using this infection model, we assessed the in vivo protective efficacy of an influenza vaccine and cross-validated the pseudovirus-based evaluation results against a live virus-infected mouse model. Our study thus establishes a safer and more convenient platform for evaluating influenza vaccine efficacy, including the assessment of broad-spectrum neutralization capacity. Full article

Background/Objectives: Influenza poses a significant risk for young children, particularly those under five. Cell culture-derived influenza vaccines offer advantages in reducing adaptive changes and mitigating egg allergy concerns. SKYCellflu^® quadrivalent has been in use since 2015, and this study aimed to assess its safety and influenza infections in children aged 6–35 months in South Korea. Methods: A prospective cohort, non-interventional, multi-center post-marketing surveillance study was conducted from 2020 to 2024. This study presents data from the 2023–2024 influenza season on safety and influenza infections in children aged 6–35 months following SKYCellflu^® vaccination. Safety was assessed based on adverse events (AEs) within 28 days post-vaccination, and influenza infections were assessed via phone calls or medical record screening. Results: Among 333 safety set participants, 54.4% reported at least one AE, with most being mild to moderate. The cumulative incidence of influenza infections among 247 ad hoc subsets was 4.5%, and the incidence rate was 1.3 per 100 person-months (95% CI, 0.7–2.4) during the 2023–2024 influenza season. The two-dose regimen in vaccine-naïve infants aged 6–11 months showed a lower cumulative incidence of influenza infection rate (0.8% vs. 3.8%) and incidence rate (0.3 vs. 0.9 per 100 person-months) than the one-dose group (3.8%). No influenza-related hospitalizations occurred within the ad hoc subset. Conclusions: This study demonstrated a tolerable safety profile and the pattern of influenza infections following SKYCellflu^® vaccination. Additionally, the two-dose regimen was associated with a lower incidence of influenza infections, suggesting potential benefits in enhancing protection among infants aged 6–11 months. Full article

Objective: Our population-based cohort study aims to compute the uptake of the influenza vaccine and the associated risk of hospitalization for respiratory diseases of infectious origin based on the residency setting and dementia status of people aged 65 or over. Methods: We conducted a retrospective cohort study on the whole population of residents aged ≥65 in Lombardy, the most populated Italian region. Using region-wide administrative data, we computed the seasonal prevalence of vaccination for influenza from 1 October 2022 to 30 April 2023. To estimate the risk of hospitalization, we applied Fine-Gray sub-distribution hazard models, accounting for the competing risk of death and adjusting for confounders. Results: Our study analyzed 2,420,279 individuals aged 65+ in Lombardy. Overall, 51.4% received an influenza vaccination in 2022–2023. Among residents living at home, 50.8% were vaccinated, while nursing home residents had an uptake of 74.0%. People living with dementia reported a vaccination coverage of 62.6%, and vaccination rates were higher among those residing in nursing homes than those who lived at home. The adjusted sub-hazard ratios (SHRs) showed higher hospitalization risks of 1.88 for unvaccinated individuals with dementia and 1.74 for unvaccinated individuals without dementia living at home. In nursing homes, the SHR for respiratory hospitalization was 2.20 for individuals without dementia and 2.40 for dementia patients. Vaccination reduced risks across all groups, but disparities persisted. Conclusions: People living with dementia were more likely to be hospitalized for respiratory diseases. However, they reported an influenza vaccination coverage that was below expectations and similar to the general population, both in nursing homes and home-living settings. Public health institutions should extend and mention dementia as a higher-risk condition. Full article

This study aimed to evaluate the humoral and cell-mediated immune responses induced by an inactivated influenza vaccine (IIV4) during the 2019/2020 influenza season in Japan. We collected blood samples from 25 healthy adults before vaccination, 2 weeks post-vaccination, and 5 months post-vaccination. Humoral and cell-mediated immunities were assessed based on hemagglutination inhibition antibody titers and interferon-γ (IFN-γ) levels, respectively. The geometric mean titer ratio for A/H3N2 exceeded 2.5, meeting the criteria outlined by the European Medicines Agency guidelines; other strains did not achieve similar thresholds. IFN-γ responses indicated significant activation for all strains, with 32–36% of participants exhibiting ≥ 1.5-fold increases. Due to the implementation of infection control measures against COVID-19, influenza activity was not observed during the 2020/2021 and 2021/2022 seasons, potentially altering influenza immunity. Our findings highlight the importance of both humoral and cell-mediated immunity in evaluating vaccine immunogenicity. Full article