WHO Influenza Update N0 522
In the Northern hemisphere, activity continued to decline or remained stable in most countries with minor increases reported in a few countries in Central America and the Caribbean, Western Asia and Northern and Southwest Europe. Influenza positivity remained elevated (>10%) in parts of North America, Tropical South America and Central America and the Caribbean (predominantly A(H1N1)pdm09), Northern and Eastern Africa (all subtypes), Southwest, Northern and Eastern Europe (predominantly A(H3N2) and B viruses), Western and Southern (predominantly A(H3N2)), Southeast (predominantly A(H1N1)pdm09 and B) and Eastern Asia (predominantly A(H1N1)pdm09). Read More
Knowledge, attitude, practice, and barriers among physicians in the Middle East and North Africa region toward influenza vaccination for the high-risk group of patients: a cross-sectional study.
Trop Dis Travel Med Vaccines 2025;11, 6.
In this study, the authors conducted a multinational cross-sectional study in 21 countries in MENA region from July 10th to September 10th, 2023. Data were collected using an online self-administered survey distributed through different social media platforms. Among 2017 physicians, the majority expressed a low to medium level of knowledge about influenza vaccination, with only 4% displaying a high level of knowledge. Regarding attitude, the majority (n = 1511, 74.9%) were quite concerned. However, only 509 (25.4%) offered the vaccine to patients. The main predictors for offering the vaccine were age, male sex, living in upper-middle-income countries, having PhD degree, being a senior resident, working two to five shifts per week, working more than five shifts per week, attitude, following these practices regarding influenza vaccination with the other office staff: Encourage and offer require but do not offer, and require and offer the influenza vaccine to the office staff. The main barriers to influenza vaccination were unawareness of vaccine availability (32%), cost (25%), and forgetfulness (23.4%). Approximately half of the physicians were knowledgeable about the flu vaccine, but practice was deficient and impeded by barriers like unawareness and forgetfulness. Read More
Prevention of Cardiovascular Diseases with Standard-Dose Quadrivalent Influenza Vaccine in People Aged ≥50 Years in Australia During the 2017 A/H3N2 Epidemic.
Vaccines 2025, 13(4), 407
The authors conducted a nested, matched case–control study within the 45 and Up study, linking data from the Australian Immunization Register, NSW Admitted Patient Data Collection and Pharmaceutical Benefits Schedule. Cases were individuals hospitalized for CVD and controls were those who were hospitalized for gastrointestinal diseases. The two groups were balanced using 1:1 propensity score matching based on age group (50–64, 65–74, 75–84, and ≥85 years) and sex. After adjusting for confounders (smoking, body mass index and income), the authors calculated the adjusted odds ratio (aOR) for vaccination during the season using multivariable logistic regression. E-values were estimated to assess residual confounding. There were 10,445 (4452 cases and 5993 controls) study participants. After matching, 8904 (85.2%) were retained with a mean age of 76.4 ± 10.4 years and 58.3% men. Following adjustment for confounders, the aOR of averting a CVD hospitalization was 0.15. The estimated VE against CVD hospitalization was 85%. The authors found an E-value of 12.82, indicating strong evidence of minimal residual confounding. In the severe 2017 influenza A/H3N2 season in Australia, The authors observed a high VE in preventing cardiovascular hospitalization despite a low VE against influenza infection prevention. Improving vaccine uptake may reduce cardiovascular burden. Read More
Evaluating the impact of influenza vaccine on preventing stroke hospitalization and death in Chinese elderly hypertensive patients: A retrospective cohort study
Vaccine 2025;April 30:127004.
The effect of influenza vaccination on stroke remains controversial, particularly given the paucity of studies conducted in mainland China. Using a comprehensive database obtained from the Regional Health Information Platform, we conducted a 7-month retrospective cohort analysis of 457,887 elderly individuals residing in an eastern Chinese city. Using multivariate competing risks regression analysis, we derived subdistribution hazard ratios (sHRs) along with the corresponding 95 % confidence intervals (CIs). There was no significant difference in the proportion of hospitalizations for stroke between those who received the influenza vaccine and those who did not (7.50 per 1000 vs. 8.12 per 1000; adjusted sHR: 0.96, 95 % CI: 0.90–1.02). However, a pronounced reduction in stroke-related mortality was observed among vaccinated individuals, with a rate of 0.18 ‰ compared with 0.54 ‰ among the unvaccinated (adjusted sHR: 0.47, 95 % CI: 0.33–0.69). This study highlights the substantial role of influenza vaccination in reducing the risk of stroke-related mortality in elderly hypertensive patients. Therefore, efforts to increase influenza vaccination rates in this population are strongly encouraged. Read More
Knowledge and Attitudes of Adult Diabetic Patients Attending Primary Health Care in Bahrain about Seasonal Influenza and Influenza Vaccination – A Cross-Sectional Study
Journal of the Bahrain Medical Society 2025; 37 (1): 1-12.
A cross-sectional study was conducted between 6th and 17th February 2022 in five health centers in Bahrain. Utilizing an online calculator, a sample size of 357 was determined. The study was conducted using a convenience sampling method, which may restrict its generalizability. A self-administered questionnaire was used to assess patients’ knowledge and attitudes about seasonal influenza and influenza vaccination. A total number of 393 participants (208 males and 185 females) were enrolled in the study with a mean age 58.8 years (SD = 10.1). Most participants in the present study had poor levels of knowledge towards seasonal influenza and influenza vaccine (56.7% and 64.1%, respectively). Furthermore, advice from doctors about the importance of vaccination was the most decisive of vaccine uptake (72.9%), while patients’ perception that the vaccine is unnecessary as flu is just a minor illness was the most determinant of vaccine refusal (40.2%). A significantly strong association was found between patients’ knowledge and attitudes towards influenza vaccine uptake (P < 0.001). Additionally, the results showed that around 49.4% of the patients did not get the vaccine. Uptake of influenza vaccine was significantly higher among female participants (Odds ratio; OR = 1.8), participants with diabetes duration above 6 years (OR = 2) and participants with good, combined knowledge of influenza and its vaccine (OR = 2.9). In conclusion, this study found significant gaps in knowledge towards seasonal influenza and influenza vaccine. Nonetheless, most patients showed significant positive attitudes in favor of the vaccine. Significant association was found between patients’ knowledge and their attitudes toward influenza vaccine uptake. Urgent interventions to improve influenza vaccine uptake and knowledge are needed. Read More
The Impact of Influenza on US Working-Age Adults: Exploring the Benefits of the Recombinant Influenza Vaccine.
Clin Infect Dis. 2025 Apr 17:ciaf200.
The authorsgathered data on influenza burden, vaccine effectiveness, and VCR from the US-CDC (2012-2023, excluding 2020-2021). We conducted a retrospective analysis of the past 10 years to illustrate the influenza burden among adults 18-64 years. We performed an age-stratified analysis using prevalence of chronic conditions to assess their impact on influenza hospitalizations and deaths, and estimated reductions in hospitalizations if RIV had been used instead of SD-IIV during the study period, using an age and risk-group decision-tree model. Over the last decade, influenza caused a median of 151,021 hospitalizations (95% CI 139,750-164,130) per season among US working-age adults. Adults aged 50-64 years had 3- to 5-fold higher rates of hospitalization and death than those aged 18-49 years. The 14% of 18-49-year-olds with chronic conditions accounted for more than 28% of hospitalizations and deaths in this group. If RIV had been used instead of SD-IIV, an additional 10,000 hospitalizations could have been prevented each season in these populations. Influenza significantly impacts US working-age adults, particularly 50-64-year-olds. Increases in longevity and chronic conditions prevalence are expected, making tailored public health vaccine recommendations important to support healthy aging. Read More
Nasal delivery of killed Bacillus subtilis spores protects against influenza, RSV and SARS-CoV-2.
Front Immunol. 2025 Apr 2;16:1501907.
In vivo viral challenge murine models were used to assess the prophylactic anti-viral effects of B. subtilis spores delivered by intranasal instilling, using an optimised three-dose regimen. Multiple nasal boosting doses following intramuscular priming with SARS-CoV-2 spike protein was also tested for the capability of spores on enhancing the efficacy of parenteral vaccination. To determine the impact of spores on immune cell trafficking to lungs, we used intravascular staining to characterise cellular participants in spore-dosed pulmonary compartments (airway and lung parenchyma) before and after viral challenge. The authors found that mice pre-treated with spores developed resistance to all three pathogens and, in each case, exhibited a significant improvement in both survival rate and disease severity. Intranasal spore dosing expanded alveolar macrophages and induced recruitment of leukocyte populations, providing a cellular mechanism for the protection. Most importantly, virus-induced inflammatory leukocyte infiltration was attenuated in spore-treated lungs, which may alleviate the associated collateral tissue damage that leads to the development of severe conditions. Remarkably, spores were able to promote the induction of tissue-resident memory T cells, and, when administered following an intramuscular prime with SARS-CoV-2 spike protein, increased the levels of anti-spike IgA and IgG in the lung and serum. Taken together, the results show that Bacillus spores are able to regulate both innate and adaptive immunity, providing heterologous protection against a variety of important respiratory viruses of high global disease burden. Read More
Safety and Immunogenicity of Poultry Vaccine for Protecting Critically Endangered Avian Species against Highly Pathogenic Avian Influenza Virus, United States.
Emerg Infect Dis. 2025 Apr 15;31(6).
In 2023, an outbreak of highly pathogenic avian influenza occurred among critically endangered California condors (Gymnogyps californianus), and >21 died. We evaluated safety, immunogenicity, vaccination strategies, and correlates of antibody response of an influenza vaccine for poultry in black vultures (Coragyps atratus) and then California condors. We noted differences in antibody titers between vaccinated and unvaccinated birds (vultures p<0.004; condors p-<0.02) but no adverse effects of vaccination. All vaccinated vultures and 80% of vaccinated condors showed maximum measured antibody response within the published range associated with survival of vaccinated and virally challenged chickens. We noted weak evidence of higher antibody responses for birds given two 0.5-mL vaccines versus those given one 1-mL vaccine but no correlation between antibody titers and sex for either species or between antibody titers and bone lead concentrations in vultures. Our results prompted initiation of a vaccination program for condors that could reduce spread of this disease among highly threatened species. Read More
Influenza A hemagglutinin virus-like particles confer protection against influenza B virus infection.
Emerg Microbes Infect. 2025 Apr 15:2494702.
Influenza A hemagglutinin (HA), neuraminidase, and/or M2e-containing virus-like particles (VLPs) induce immune responses that contribute to protection against multiple influenza A virus subtypes. In this study, we investigated the protective efficacy of influenza A/H1H3 VLPs against influenza B virus infections (B/Colorado/06/2017 and B/Malaysia/2506/2004, Victoria lineage) in mice. A/H1H3 VLP immunization elicited protection against lethal challenge infections with both B/Colorado and B/Malaysia, significantly reducing lung viral loads and ensuring 100% survival of immunized mice. Sera from A/H1H3VLP-immunized mice recognized inactivated B/Colorado and B/Malaysia virus antigens and enhanced Fc receptor-mediated antibody-dependent cellular cytotoxicity (ADCC) responses. Notably, immune sera reacted with HA, HA1, and HA2 antigens from both B/Colorado and B/Malaysia viruses. A/H1H3VLP immunization also induced lung IgG and IgA antibody responses against HA, HA1, and HA2 of both B viruses, as well as antibody-secreting cell responses (ASC), germinal center B (GC B) responses, and CD4+ T cell responses. Additionally, A/H1H3VLP immunization significantly suppressed pro-inflammatory cytokines responses (IFN-γ, IL-6). These results suggest that A/H1H3 VLP hold promise as a candidate for a universal influenza vaccine capable of providing cross-protection against influenza B virus infection. Read More
Excess Respiratory Hospitalisations Associated with Influenza, Respiratory Syncytial Virus and SARS-CoV-2 in Singapore from 2015 to 2023
Influenza Other Respi Viruses, 19: e70098.
The patterns of circulation and burden of influenza and respiratory syncytial virus (RSV) in Singapore are affected by the COVID-19 pandemic containment measures. These patterns in relation to SARS-CoV-2 in a post-pandemic era are unclear. Using data from 2015 to 2023, the authors estimated excess influenza-, RSV- and SARS-CoV-2-associated hospitalisation in Singapore, adjusted for rhinovirus/enterovirus activity in generalised additive models. The data include pneumonia and influenza (P&I) hospitalisation from a national inpatient database and a community-wide acute respiratory infection (ARI) sentinel surveillance programme, stratified by age groups. Across all age groups, the proportion of hospitalisation associated with influenza, SARS-CoV-2 and RSV was 13.2% (95% CI 5.0%–21.6%), 19.3% (95% CI 13.8%–25.0%) and 4.0% (95% CI 0.9%–12.1%) in 2023, respectively. From 2019 to 2023, all-age influenza-associated hospitalisation declined from 264.4 per 100,000 person-years (95% CI 214.2–313.2) to 203.7 per 100,000 person-years (95% CI 76.8–333.6). In contrast, all-age RSV-associated hospitalisation after the pandemic was 62.2 per 100,000 person-years (95% CI 13.8–186.9), similar to pre-pandemic observations. Peak seasonal influenza occurred 3–8 weeks later as compared with the time of pre-pandemic peak influenza activity. The overall burden of influenza has declined after the COVID-19 pandemic and its burden is comparable with SARS-CoV-2. Furthermore, shifts in the timing of peak influenza activity suggest a potential need to review the timing of vaccine recommendations in Singapore. Read More
Independent effect of influenza vaccination on all-cause mortality in critically ill patients with atrial fibrillation: A retrospective study from the MIMIC-IV database.
Int J Cardiol. 2025 Apr 11:133246.
Atrial fibrillation (AF) is common in critically ill patients and associated with higher mortality. The impact of influenza vaccination on all-cause mortality in this population is unclear. This study evaluates the effect of influenza vaccination on mortality in critically ill AF patients. A retrospective cohort analysis was conducted using the MIMIC-IV database. The effect of influenza vaccination on mortality was assessed using Kaplan-Meier survival curves and Cox proportional hazards models, adjusted for confounders. Inverse probability of treatment weighting (IPTW) and propensity score matching (PSM) were used to minimize selection bias. Subgroup analyses examined clinical characteristics among AF patients in the intensive care unit (ICU). Among 12,137 ICU AF patients, 6554 (54.0 %) received the influenza vaccine. Vaccination was associated with reduced all-cause mortality (28-day hazard ratio [HR] = 0.79, 90-day HR = 0.83, 365-day HR = 0.84; all p-values <0.001). After PSM and covariate adjustment, influenza vaccination remained an independent predictor of better outcomes (28-day HR = 0.83, 90-day HR = 0.82, 365-day HR = 0.84; all p-values <0.001). These findings were consistent in IPTW analyses. Subgroup analyses showed greater benefits in elderly, hypertensive, and non-paroxysmal AF patients. Influenza vaccination is associated with improved survival in critically ill AF patients. These findings support vaccination as a crucial protective measure for high-risk AF patients in the ICU. Read More