WHO Influenza Update N0 520
In the Northern hemisphere, activity continued to decline or remained the same in most countries. Minor increases in activity were reported in a few countries in Central America and Caribbean, Southwest and Eastern Europe, and Western, Southern and South-East Asia. Influenza positivity remained elevated (>10%) in the Americas (predominantly A(H1N1)pdm09 and A(H3N2)), Western (predominantly A(H1N1)pdm09) and Northern Africa (predominantly A(H3N2) and B viruses), Southwest and Northern Europe (A and B viruses in similar proportions), Eastern Europe (predominantly B viruses), Western and Southern Asia (predominantly A(H3N2) and B viruses), Central Asia (predominantly B viruses) and South-East Asia (predominantly A(H1N1)pdm09). Read More
Optimizing Influenza Vaccine Allocation by Age Using Cost-Effectiveness Analysis: A Comparison of 6720 Vaccination Program Scenarios in Children and Adults in Belgium.
Epidemics 2025; April 5:100826
Many European countries prioritize groups for annual influenza vaccination based on risk of severe disease and death resulting in relatively high influenza vaccination coverage in older adults in Belgium. However, coverage is much lower in younger adults and negligible in children. Children and young adults are known to play a major role in the transmission dynamics of influenza. Thus, an important policy question is how influenza vaccines can be optimally allocated across age groups, taking indirect effects into account. The authors adapted a dynamic transmission model to reproduce influenza seasonality in Belgium comparing 6,720 mutually exclusive vaccination options, including current practice. They concluded that overall QALY gains can be maximized in seasonal influenza vaccination programs at acceptable costs by achieving high vaccination coverage in childhood age groups. Read More
To limit bird flu spread, keep wild birds away from poultry, livestock Waterfowl Alert Network data help assess the risk of avian influenza H5N1.
California Agriculture 2025;79:1
Every winter, millions of migratory birds fly south to warmer locales, passing over California Central Valley dairies and poultry farms. Many of these wild waterfowl are carrying the virus that causes avian influenza, based on the U S. Department of Agriculture’s (USDA) wild-bird surveillance, says Maurice Pitesky, University of California Cooperative Extension poultry specialist in the School of Veteri-nary Medicine at UC Davis. Bird flu has killed millions of birds and disrupted milk and poultry production. In California, highly pathogenic avian influenza H5N1 has been detected in commercial and backyard flocks of poultry and dairy cows and, more recently, poultry and dairy workers have become infected. To contain the disease, USDA is testing milk for the avian influenza H5N1 virus and farmers are sup-plying poultry and dairy workers with personal pro-tective equipment. To avert future outbreaks of avian influenza from infecting livestock, Pitesky recommends reducing the overlap of waterfowl habitat with farms that raise animals. This would help prevent birds from mingling with the domestic animals and passing the virus to cows, pigs and poultry. Read More
Effectiveness of Influenza Vaccination in Children Aged 6 to 59 Months during the Inaugural 2022-2023 Season in Andalusia, Spain
J Pediatrics 2025;March 21:114558
Population-based, retrospective cohort study during the 2022-2023 influenza season of 287,661 children aged 6 to 59 months at the beginning of the inaugural 2022-2923 vaccination campaign. Adjusted vaccine effectiveness (VE) was calculated by estimating multivariable logistic regression models for likelihood of influenza diagnosis in vaccinated and unvaccinated children. In children aged 6 to 59 months, VE was 51% (95% CI: 48-53%) for preventing infection and 69% (95% CI: 56-79%) for preventing influenza-related hospitalization. In children aged 6 to 23 months, VE was 53% (95% CI: 48-57%) for preventing influenza and 76% (95% CI: 57-87%) for preventing hospitalization due to influenza. In both subpopulations, VE was significantly higher with the two-dose vaccination schedule. Influenza vaccination shows moderate effectiveness in preventing influenza and high effectiveness in preventing influenza-related hospitalization in children aged 6 to 59 months. This highlights the importance of strengthening influenza vaccination coverage in this age group. Read More
Vaccines under attack
Insight (Australia) April 7, 2025
The World Health Organization (WHO) estimates that the use of vaccines prevents 4 to 5 million deaths annually, and with better global vaccination coverage, this number could increase significantly. The historical successes of vaccination campaigns are best known for the eradication and/or control of (now forgotten) deadly infectious diseases such as smallpox, which claimed millions of lives and was eradicated in 1980 through a concerted global vaccination campaign. Poliomyelitis too has been almost eradicated globally with cases markedly reduced since 1988 due to the efforts of many organisations, including the WHO, Rotary International, the Global Polio Eradication Initiative, and the Bill & Melinda Gates Foundation. Read More
Patterns in prescribing and dispensing of influenza antivirals among adults with influenza presenting to urgent care and emergency department settings, VISION Network, 2023–2024.
Clin Infectious Disease 2025; April 5: ciaf178
A retrospective cross-sectional study was conducted for encounters from four large, integrated health systems participating in the VISION network of adult patients presenting with acute respiratory illness to urgent cares or emergency departments and with positive influenza virus test results during the 2023–2024 influenza season. A total of 10,700 patient encounters were eligible for analysis. Among encounters with a positive standard molecular influenza test result (N=5,231), 58% (range across sites: 47–64%) were prescribed antivirals, with 67% of prescribing occurring on the encounter date. Among those prescribed antivirals (N=3,050), 80% (range across sites: 75–91%) had them dispensed, with 65% of dispensing occurring on the prescription date. Encounters among persons aged ≥65 years had lower odds of same-day prescribing (0.57 [95% CI: 0.42–0.78]) and lower odds of same-day dispensing (0.58 [95% CI: 0.36–0.94]) compared to those 18–49 years. Gaps in antiviral treatment within urgent care and emergency department settings remain for patients at higher risk of influenza complications, notably among older adults. Strategies to improve earlier initiation of antiviral treatment may help reduce the risk of influenza-associated complications. Read More
Live-attenuated pandemic H1N1 influenza vaccines expressing computationally optimized broadly reactive antigens (COBRAs) are immunogenic and protective in mice and ferrets.
Vaccine 2025;53 (April 19):127090
Computationally optimized broadly reactive antigens (COBRAs) induce broad and protective immune responses across multiple viral vaccine platforms. However, their suitability for incorporation into live attenuated influenza vaccines (LAIVs) remains uncertain, as antigen modifications could potentially impact LAIV generation, replication, stability, or immunogenicity. In this study, COBRA hemagglutinin (HA) and neuraminidase (NA) antigens designated Y2 and N1_I, respectively, of the influenza H1N1 subtype were reverse-engineered into A/Puerto Rico/8/1934 (PR8)-based LAIVs. The impact of HA stability and NA composition on LAIV properties was evaluated in cell culture, mice, and ferrets. COBRA LAIV yields were higher in MDCK cells compared to Vero cells, and a higher HA activation pH was associated with increased LAIV growth in cell culture. The COBRA LAIVs elicited broad antibody responses against pandemic H1N1 viruses and provided robust protection in both mice and ferrets. The standard COBRA LAIV, containing unmodified HA Y2 and NA N1_I, had virus inactivation pH and HA activation pH values of 5.4 and 5.6, respectively. In contrast, a modified COBRA LAIV, containing an HA2-K153E mutation and NA from the vaccine strain A/Hawaii/70/2019 (HI19), had a virus inactivation pH of 5.3 and an elevated HA activation pH of 6.0. This modified LAIV had improved growth in cell culture and greater protection from challenge virus lung titers in elderly ferrets. Read More
Influenza A(H1N1)pdm09 Virus with Reduced Susceptibility to Baloxavir, Japan, 2024.
Emerg Infect Dis. 2025 Apr 3;31(5)
Influenza A(H1N1)pdm09 virus carrying an I38N substitution was detected in an untreated teenager in Japan. The I38N mutant virus exhibited reduced susceptibility to baloxavir but remained susceptible to neuraminidase inhibitors and showed reduced growth capability. Monitoring antiviral drug susceptibility of influenza viruses is necessary to aid public health planning and clinical recommendations. Read More
Impact of intensive health education on influenza vaccination and acute exacerbations in outpatients with chronic obstructive pulmonary disease: a real-world study.
J Glob Health. 2025;15:04047
Participants were from the Real World Research of Diagnosis and Treatment of COPD study, a real-world prospective cohort study. COPD patients were included from December 2016 to April 2023 and followed up for one year. In January 2022, clinicians began strengthening health education for outpatients with COPD. We identified patients visiting the clinic from January 2022 to April 2023 as the intensive health education group and those visiting from December 2016 to December 2021 as the control group. We analysed factors associated with influenza vaccination and the effect of influenza vaccine on acute exacerbations by multivariate analysis. 7834 patients were included. Compared with the control group, the intensive health education group had a higher rate of influenza vaccination (1.6% vs. 12.2%, P < 0.01). Smoking cessation, high school education or above, influenza vaccination in the past year and intensive health education were independently associated with influenza vaccination. Influenza vaccination reduced the incidence of future acute exacerbations (adjusted odds ratio (aOR) = 0.48; P < 0.01), frequent acute exacerbations (aOR = 0.47; P = 0.01), and severe acute exacerbation (aOR = 0.38; P < 0.01) in COPD patients. Influenza vaccination reduced the risk of future acute exacerbations in patients with COPD. Clinician-led intensive health education can improve the influenza vaccination of outpatients with COPD, and clinicians and policymakers should pay attention to and apply this method. Read More
Acute Respiratory Viral Infections Among Adult Patients in Edirne, Turkey.
Trop Med Infect Dis. 2025 Feb 19;10(2):58.
The study included 764 adult patients (aged 18 and older) diagnosed with influenza symptoms. Respiratory viral samples were collected and analyzed for COVID-19, influenza A and B, and RSV using Multiplex PCR, with results evaluated retrospectively. Continuous variables in the study were compared using a t-test, and categorical variables were compared with a chi-square test. A logistic regression analysis was performed for the analysis of COVID-19. In this analysis, PCR positivity was the dependent variable, while age, gender, and humidity level served as independent variables. COVID-19 PCR positivity was detected in 142 patients (18.6%), with INF-A (influenza A) in 13 (3.7%), INF-B (influenza B) in 15 (4.2%), and RSV in 2 (0.6%). Higher humidity (over 60%) was associated with reduced viral PCR positivity rates for COVID-19 and influenza B, while low (up to 40%)/normal (40-60%) humidity correlated with positivity rate (p < 0.05 for both). Logistic regression analysis indicated that high humidity levels offer protection against COVID-19 (OR: 0.356; 95% CI: 0.245-0.518). Read More
Characteristics of Influenza A/H1N1 complications: ARDS, pneumonia, acute kidney failure, sepsis – review
J Education Health Sport 2025; 7 April 2025. Vol. 80, p. 58075.
Type A H1N1 influenza got its start in 2009 during a pandemic that swept across many countries and contributed to massive mortality. It was characterised by its prevalence among young adults and children.
It was associated with fairly common symptoms such as cough, fever and muscle aches, yet it spread rapidly and caused many complications, mainly involving the respiratory system, but also the nervous, circulatory and urinary systems. They often led to long hospital stays and differed in their course and clinical picture from the same diseases of other aetiologies. Read More