Seasonal Epidemics Research Articles

Evaluation of FluSight influenza forecasting in the 2021–22 and 2022–23 seasons with a new target laboratory-confirmed influenza hospitalizations

Accurate forecasts can enable more effective public health responses during seasonal influenza epidemics. For the 2021–22 and 2022–23 influenza seasons, 26 forecasting teams provided national and jurisdiction-specific probabilistic predictions of weekly confirmed influenza hospital admissions for one-to-four weeks ahead. Forecast skill is evaluated using the Weighted Interval Score (WIS), relative WIS, and coverage. Six out of 23 models outperform the baseline model across forecast weeks and locations in 2021–22 and 12 out of 18 models in 2022–23. Averaging across all forecast targets, the FluSight ensemble is the 2nd most accurate model measured by WIS in 2021–22 and the 5th most accurate in the 2022–23 season. Forecast skill and 95% coverage for the FluSight ensemble and most component models degrade over longer forecast horizons. In this work we demonstrate that while the FluSight ensemble was a robust predictor, even ensembles face challenges during periods of rapid change.

Assessment of Epidemiological Trend of Influenza-Like Illness in Italy from 2010/2011 to 2023/2024 Season: Key Points to Optimize Future Vaccination Strategies against Influenza.

Seasonal influenza is an acute respiratory infectious disease due to influenza viruses, causing a relevant number of illnesses and deaths each year worldwide. Influenza is a preventable disease by vaccination. The aim of this study was to assess the epidemiology of seasonal influenza in Italy through the analysis of data from the epidemiological and virological RespiVirNet surveillance system for the season 2010/2011 to 2023/2024 to identify the epidemiological key points to plan the most appropriate vaccination strategies. The cumulative and maximum weekly incidence of influenza-like illness (ILI) and epidemic period (beginning, end, duration in weeks) were assessed in the pre-pandemic period (2010/2011-2019/2020) and they were compared to the pandemic and post-pandemic one. In all seasons, children reported the highest incidence values of ILI and longer epidemic periods in contrast with the older population. The epidemic seasons 2020/2021 and 2021/2022 had abnormal trends while in the last seasons 2022/2023 and 2023/2024 the epidemiological and virological trends of ILI were confirmed as reported in the pre-pandemic period but with high intensity. Influenza virus A was predominant: the H3N2 subtype circulated more than virus H1N1pdm09. In the few seasons when influenza virus B was the most frequent influenza agent, it co-circulated with influenza virus A. The monitoring of cases is the fundamental tool to better understand the epidemiology of influenza and to optimize future preventive strategies.

ATAGI targeted review 2023: Vaccination for preventing influenza in Australia.

Annual seasonal influenza epidemics cause substantial disease and economic burden worldwide. During the coronavirus disease 2019 (COVID-19) pandemic in 2020 and 2021, influenza activity significantly declined. However, influenza resurged in Australia following the relaxation of non-pharmaceutical interventions, with increased influenza virus circulation in early 2022 coinciding with the SARS-CoV-2 Omicron BA.2 variant wave. Together with other respiratory virus diseases, these disease impacts on the Australian population and healthcare system have re-emphasised the importance of influenza vaccination and control. We aim to provide an overview of the current seasonal influenza vaccination program in Australia and summarise evidence and considerations underpinning potential future immunisation strategies. Influenza causes disproportionately higher morbidity and mortality in young children and older adults. Other populations at elevated risk from influenza include Aboriginal and Torres Strait Islander peoples, pregnant women, and people with certain underlying medical conditions. All Australians aged ≥ 6 months are recommended to receive influenza vaccine every year. The National Immunisation Program (NIP) provides free vaccine for eligible at-risk populations. While approximately 70% of older adults had received influenza vaccine in 2022, coverage in other age groups remains suboptimal. There are several key unmet needs and challenges, but also potential strategies for enhancing the influenza vaccination program in Australia. Improved monitoring and evaluation, including the use of relevant linked datasets for such purposes, is imperative to better understand variations in coverage and vaccination impact in specific populations. Adoption of evidence-based strategies, such as culturally appropriate resources that consider the characteristics of diverse Australian populations, may also help to achieve higher vaccine coverage rates. Additionally, greater vaccine uptake across the population could be facilitated by expanding the NIP-eligible population where cost-effective, and adopting the use of more effective and different types of vaccines when available.

Occurrence of Circulating Antibodies against the Hemagglutinins of Influenza Viruses in the 2022/2023 Epidemic Season in Poland.

The aim of this study was to determine the level of anti-hemagglutinin antibodies in blood sera collected from patients during the 2022/2023 epidemic season in Poland. A total of 700 sera samples from patients across the country were tested. The samples were divided into seven groups according to the age of the patients, with 100 samples from each age group. The hemagglutination inhibition test (OZHA) was used to determine the level of anti-hemagglutinin antibodies. The test results have confirmed the presence of anti-hemagglutinin antibodies for antigens A/Victoria/2570/2019 (H1N1)pdm09, A/Darwin/9/2021 (H3N2), B/Austria/1359417/2021 (B/Yamagata lineage) and B/ Phuket/3073/2013 (B/Victoria lineage) present in the influenza vaccine recommended by the World Health Organization (WHO) for the 2022/2023 epidemic season. The highest geometric mean antibody titres (GMT) and protection rate values (%) were recorded for hemagglutinin A/H3N2. In Poland, in the 2022/2023 epidemic season, the percentage of the population vaccinated against influenza was 5.7%. Therefore, the test results can be interpreted as the response of the immune system in patients who have been previously infected with an influenza virus.

Epidemiological and clinical characteristics of respiratory syncytial virus infection among people aged 60 and above in Beijing City

Objective: To investigate the epidemiological and clinical characteristics of RSV among patients aged ≥60 years in Beijing from 2015 to 2023. Methods: Based on the respiratory pathogen surveillance system, samples of upper respiratory tract infections (URTI), non-severe community-acquired pneumonia (nsCAP) and severe community-acquired pneumonia (sCAP) among people aged ≥60 years were collected from 28 sentinel hospitals in 16 districts of Beijing from January 2015 to December 2023. Swab samples were collected from URTI within one week, and lower respiratory tract samples from nsCAP and sCAP were collected. Demographic and epidemiological data were also collected. Various respiratory pathogens including RSV were detected. Results: From January 2015 to December 2023, a total of 20 349 cases of acute respiratory infections aged ≥60 years were included, with the RSV-positive rate of 1.54% (313/20 349, 95%CI: 1.39%-1.68%). Among them, the total RSV-positive rates of older people during the pre-pandemic, pandemic, and post-pandemic periods of COVID-19 were 1.59% (207/13 006, 95%CI: 1.38%-1.81%), 0.82% (38/4 650, 95%CI: 0.56%-1.08%) and 2.53% (68/2 693, 95%CI: 1.93%-3.12%), respectively. The difference in RSV-positive rate was statistically significant (P<0.001). Based on the sampling time of cases, the RSV epidemic season for older people in Beijing was from October to March of the following year, with a peak period in December or January of the following year. In the post COVID-19 pandemic, there were very few RSV-positive cases detected in the elderly from April to June 2023, with only one positive case detected in May and one in June. The RSV-positive rate of older people increased significantly from October to December, reaching 11.75% (51/383) in December. Among 263 RSV-positive cases in the elderly, RSV-A, RSV-B and unclassified type accounted for 43.35% (114/263), 29.28% (77/263) and 27.38% (72/263), respectively. Since 2020, there has been a subtype conversion, with RSV-B being the main focus. Among 197 elderly cases that have complete clinical data, the main symptoms were cough (86.8%, 171/197), sputum (80.2%, 158/197) and fever (73.60%, 145/197). About 24.87% (49/197) of elderly cases experienced complications. The hospitalization mortality rate was 4.57% (9/197), and the hospitalization rate was 78.68% (155/197). The ICU occupancy rate was 1.99% (36/197). The mechanical ventilation usage rate was 13.32% (33/197), and the length of hospital stay [M (Q1, Q3)] was 12 (9, 16) days. Conclusion: In Beijing, the RSV infection rate is relatively low during the COVID-19 pandemic, and the prevalence of COVID-19 is relatively high. In 2023, there was no out-of-season outbreak of RSV infection among the elderly. Elderly RSV infection cases have multiple complications, severe diseases, and poor prognosis.

Host Innate Antiviral Response to Influenza A Virus Infection: From Viral Sensing to Antagonism and Escape.

Influenza virus possesses an RNA genome of single-stranded, negative-sensed, and segmented configuration. Influenza virus causes an acute respiratory disease, commonly known as the "flu" in humans. In some individuals, flu can lead to pneumonia and acute respiratory distress syndrome. Influenza A virus (IAV) is the most significant because it causes recurring seasonal epidemics, occasional pandemics, and zoonotic outbreaks in human populations, globally. The host innate immune response to IAV infection plays a critical role in sensing, preventing, and clearing the infection as well as in flu disease pathology. Host cells sense IAV infection through multiple receptors and mechanisms, which culminate in the induction of a concerted innate antiviral response and the creation of an antiviral state, which inhibits and clears the infection from host cells. However, IAV antagonizes and escapes many steps of the innate antiviral response by different mechanisms. Herein, we review those host and viral mechanisms. This review covers most aspects of the host innate immune response, i.e., (1) the sensing of incoming virus particles, (2) the activation of downstream innate antiviral signaling pathways, (3) the expression of interferon-stimulated genes, (4) and viral antagonism and escape.

Variability in the Timing of Respiratory Syncytial Virus Epidemics in Guatemala, 2008-2018.

The description of local seasonality patterns in respiratory syncytial virus (RSV) incidence is important to guide the timing of administration of RSV immunization products. We characterized RSV seasonality in Guatemala using the moving epidemic method (MEM) with absolute counts of RSV-associated acute respiratory infections (ARI) from hospital surveillance in Santa Rosa and Quetzaltenango departments of Guatemala. From Week 17 of 2008 through Week 16 of 2018, 8487 ARI cases tested positive for RSV by rRT-PCR. Season onsets varied up to 5 months; early seasons starting in late May to early August and finishing in September to November were most common, but late seasons starting in October to November and finishing in March to April were also observed. Both epidemic patterns had similar durations ranging from 4 to 6 months. Epidemic thresholds (the levels of virus activity that signal the onset and end of a seasonal epidemic) calculated prospectively using previous seasons' data captured between 70% and 99% of annual RSV detections. Onset weeks differed by 2-10 weeks, and offset weeks differed by 2-16 weeks between the two surveillance sites. Variability in the timing of seasonal RSV epidemics in Guatemala demonstrates the difficulty in precisely predicting the timing of seasonal RSV epidemics based on onset weeks from past seasons and suggests that maximal reduction in RSV disease burden would be achieved through year-round vaccination and immunoprophylaxis administration to at-risk infants.

HnRNPAB inhibits Influenza A virus infection by disturbing polymerase activity

Influenza A virus (IAV) continuously poses a considerable threat to global health through seasonal epidemics and recurring pandemics. IAV RNA-dependent RNA polymerases (FluPol) mediate the transcription of RNA and replication of the viral genome. Searching for targets that inhibit viral polymerase activity helps us develop better antiviral drugs. Here, we identified heterogeneous nuclear ribonucleoprotein A/B (hnRNPAB) as an anti-influenza host factor. hnRNPAB interacts with NP of IAV to inhibit the interaction between PB1 and NP, which is dependent on the 5-amino-acid peptide of the hnRNPAB C-terminal domain (aa 318–322). We further found that the 5-amino-acid peptide blocks the interaction between PB1 and NP to destroy the FluPol activity. In vivo studies demonstrate that hnRNPAB-deficient mice display higher viral burdens, enhanced cytokine production, and increased mortality after influenza infection. These data demonstrate that hnRNPAB perturbs FluPol complex conformation to inhibit IAV infection, providing insights into anti-influenza defense mechanisms.

A two-tiered high-flow nasal cannula approach does not increase intensive care utilization and hospital length of stay in bronchiolitis

While concerns about high-flow nasal cannula oxygen (HFNC) overuse and associated increased use of hospital resources are rapidly spreading, a two-tiered approach in its use is recommended by recent bronchiolitis guidelines. However, data on its effects in practice have not been reported. We aimed to analyze the trends in use of HFNC, hospitalizations, length of stay (LOS), and intensive care unit (ICU) admissions for bronchiolitis in a tertiary care center using a two-tiered HFNC approach since its introduction in practice. We retrospectively included data of children < 12 months of age who presented to the Paediatric Emergency Department (PED) and were hospitalized for bronchiolitis at our institution in the epidemic season between October 1st and April 30th during the years 2012–2023 and compared the clinical data across the years. Of the 687 hospitalized children included, 79.9% required oxygen supplementation. Use of HFNC significantly increased since its implementation (from 25% in 2012–2013 to over 60% since 2019–2020, p < 0.0001) and was most frequently administered as rescue treatment (in 57.5% of patients). There was no increased trend in ICU admissions (between 1.5% and 10.0% of hospitalizations across seasons, p = 0.40), while LOS, after increasing between 2013 and 2016 (medians between 4.0 and 5.4 days), remained stable thereafter (medians between 3.8 and 4.3 days).Conclusions: The use of HFNC according to a two-tiered approach does not appear to be associated with an increase in ICU utilization or LOS.What is Known:• Bronchiolitis is one of the most common reasons for hospitalization in infants.• Use high-flow nasal canulae oxygen (HFNC) has rapidly spread outside the intensive care unit (ICU) to treat infants with bronchiolitis, although increasing evidence has dampened the initial enthusiasm about their effectiveness.• Concerns nowadays are rising about HFNC overuse and associated increased use of hospital resources, including escalation of care to ICU.What is New:• A more selective use of HFNC according to a “two-tiered approach”, intended as a second-line rescue treatment in non-severely ill children who fail standard oxygen therapy, is not associated with increased ICU and length of hospital stay.

Infection prevention and control in Dutch general practices before and during the COVID-19 pandemic and its implications for pandemic preparedness and seasonal respiratory epidemics: a qualitative study on lessons learned

BackgroundThe COVID-19 pandemic has prompted a re-evaluation of infection prevention and control (IPC) in general practices, highlighting the need for comprehensive IPC implementation. This study aimed to evaluate healthcare workers’ (HCWs) experiences and perspectives regarding IPC in general practices before and during the COVID-19 pandemic, and its implications for post-pandemic IPC implementation.MethodsThis qualitative study involved semi-structured, in-depth interviews during two time periods: (1) prior to the COVID-19 pandemic (July 2019-February 2020), involving 14 general practitioners (GPs) and medical assistants; and (2) during the COVID-19 pandemic (July 2022-February 2023), including 22 GPs and medical assistants. Data analysis included thematic analysis that addressed multiple system levels.ResultsFindings indicated a shift towards comprehensive IPC implementation and organisation during the pandemic compared to the pre-pandemic period. Since the Omicron variant, some general practices maintained a broad set of IPC measures, while others released most measures. HCWs’ future expectations on post-pandemic IPC implementation varied: some anticipated reduced implementation due to the desire to return to the pre-pandemic standard, while others expected IPC to be structurally scaled up during seasonal respiratory epidemics. Main contextual challenges included patient cooperation, staff shortages (due to infection), shortages of IPC materials/equipment, and frequently changing and ambiguous guidelines. Key lessons learned were enhanced preparedness (e.g., personal protective equipment supply), and a new perspective on care organisation (e.g., digital care). Main recommendations reported by HCWs were to strengthen regional collaboration within primary care, and between primary care, public health, and secondary care.ConclusionHCWs’ experiences, perspectives and recommendations provide insights to enhance preparedness for future epidemics and pandemics, and sustain IPC in general practices. For IPC improvement strategies, adopting an integrated system-based approach that encompasses actions across multiple levels and engages multiple stakeholders is recommended.

The Hospital Burden of Flu in Italy: a retrospective study on administrative data from season 2014–2015 to 2018–2019

BackgroundEvery year in Italy, influenza affects about 4 million people. Almost 5% of them are hospitalised. During peak illness, enormous pressure is placed on healthcare and economic systems. This study aims to quantify the clinical and economic burden of severe influenza during 5 epidemic seasons (2014–2019) from administrative claims data.MethodsPatients hospitalized with a diagnosis of influenza between October 2014, and April 2019, were analyzed. Clinical characteristics and administrative information were retrieved from health-related Administrative Databases (ADs) of 4 Italian Local Health Units (LHUs). The date of first admission was set as the Index Date (ID). A follow-up period of six months after ID was considered to account for complications and re-hospitalizations, while a lookback period (2 years before ID) was set to assess the prevalence of underlying comorbidities.ResultsOut of 2,333 patients with severe influenza, 44.1% were adults ≥ 65, and 25.6% young individuals aged 0–17. 46.8% had comorbidities (i.e., were at risk), mainly cardiovascular and metabolic diseases (45.3%), and chronic conditions (24.7%). The highest hospitalization rates were among the elderly (≥ 75) and the young individuals (0–17), and were 37.6 and 19.5/100,000 inhabitants/year, respectively. The average hospital stay was 8 days (IQR: 14 − 4). It was higher for older individuals (≥ 65 years, 11 days, [17 − 6]) and for those with comorbidities (9 days, [16 − 6]), p-value < 0.001. Similarly, mortality was higher in elderly and those at risk (p-value < 0.001). Respiratory complications occurred in 12.7% of patients, and cardiovascular disorders in 5.9%. Total influenza-related costs were €9.7 million with hospitalization accounting for 95% of them. 47.3% of hospitalization costs were associated with individuals ≥ 65 and 52.9% with patients at risk. The average hospitalisation cost per patient was € 4,007.ConclusionsThis retrospective study showed that during the 2014–2019 influenza seasons in Italy, individuals of extreme ages and those with pre-existing medical conditions, were more likely to be hospitalized with severe influenza. Together with complications and ageing, they worsen patient’s outcome and may lead to a prolonged hospitalization, thus increasing healthcare utilization and costs. Our data generate real-world evidence on the burden of influenza, useful to inform public health decision-making.

Epidemic Characteristics and Meteorological Risk Factors of Hemorrhagic Fever With Renal Syndrome in 151 Cities in China From 2015 to 2021: Retrospective Analysis.

Hemorrhagic fever with renal syndrome (HFRS) continues to pose a significant public health threat to the population in China. Previous epidemiological evidence indicates that HFRS is climate sensitive and influenced by meteorological factors. However, past studies either focused on too-narrow geographical regions or investigated time periods that were too early. There is an urgent need for a comprehensive analysis to interpret the epidemiological patterns of meteorological factors affecting the incidence of HFRS across diverse climate zones. In this study, we aimed to describe the overall epidemic characteristics of HFRS and explore the linkage between monthly HFRS cases and meteorological factors at different climate levels in China. The reported HFRS cases and meteorological data were collected from 151 cities in China during the period from 2015 to 2021. We conducted a 3-stage analysis, adopting a distributed lag nonlinear model and a generalized additive model to estimate the interactions and marginal effects of meteorological factors on HFRS. This study included a total of 63,180 cases of HFRS; the epidemic trends showed seasonal fluctuations, with patterns varying across different climate zones. Temperature had the greatest impact on the incidence of HFRS, with the maximum hysteresis effects being at 1 month (-19 ºC; relative risk [RR] 1.64, 95% CI 1.24-2.15) in the midtemperate zone, 0 months (28 ºC; RR 3.15, 95% CI 2.13-4.65) in the warm-temperate zone, and 0 months (4 ºC; RR 1.72, 95% CI 1.31-2.25) in the subtropical zone. Interactions were discovered between the average temperature, relative humidity, and precipitation in different temperature zones. Moreover, the influence of precipitation and relative humidity on the incidence of HFRS had different characteristics under different temperature layers. The hysteresis effect of meteorological factors did not end after an epidemic season, but gradually weakened in the following 1 or 2 seasons. Weather variability, especially low temperature, plays an important role in epidemics of HFRS in China. A long hysteresis effect indicates the necessity of continuous intervention following an HFRS epidemic. This finding can help public health departments guide the prevention and control of HFRS and develop strategies to cope with the impacts of climate change in specific regions.

Dynamic vaccination strategies in dual-strain epidemics: A multi-agent-based game-theoretic approach on scale-free hybrid networks

This paper proposes a multi-agent-based game-theoretic framework to explore the dynamics of decision-making among agents in a situation involving a dual-strain epidemic, where the emergence of the second strain is directly related to the first strain. It considers the impact of imperfect vaccination on dual strains within the SIRV framework, in a hybrid network that combines scale-free and grid-based structures. This research presents three models based on the level of decision-making of agents: Individual Decision Making (IDM), Collective Decision Making (CDM), and Stochastic Decision Making (SDM) model. In the IDM model, agents can continuously update their strategies based on the infection and vaccination statuses of their immediate neighbors. The CDM model offers a macro-level approach where agents’ willingness to vaccinate varies uniformly, while the SDM model maintains a constant level of willingness for vaccination across agents. This study demonstrates that agents using the IDM model tend to initiate vaccination earlier in scenarios of high infection rates, effectively mitigating the spread of the disease in subsequent epidemic seasons. However, when both infection and vaccination rates heavily influence decision-making, there is a noticeable decrease in vaccination uptake, thereby aggravating the spread of infection. Additionally, the authors found that in scenarios of high infection, an over reliance on vaccination without adequate initial uptake can jeopardize disease control efforts. Another important finding of this study is that despite the CDM and SDM models showing a quicker emergence of the second strain and reaching equilibrium points faster than the IDM model, the overall infection rate remains lower in the IDM model. This research underscores the complexity of managing dual-strain epidemics through vaccination strategies and highlights the significance of micro-level decision-making in epidemic control.

SARS-CoV-2 and influenza vaccine hesitancy during the COVID-19 pandemic in a dynamic perspective

ABSTRACT To investigate the dynamic evolution of vaccine hesitancy toward both COVID-19 and influenza in a context characterized by the compresence of SARS-CoV-2 pandemic and seasonal flu epidemics, a two times repeated cross-sectional exploratory design was performed at Udine Hospital (Italy) following a cohort of 479 adult patients with a previous history of SARS-CoV-2 infection in 2020. Vaccine attitude was assessed through standardized telephone interviews performed at 12 and 18 months after the acute illness. The first interview reported the success of the 2020/21 seasonal influenza immunization with 46.8% (224/479) of the participants showing a positive attitude, especially the elderly and people with comorbidities (p < .001), but the investigation conducted at 18 months showed a drastic drop in flu shot acceptance (30/166, 18.1%). On the other hand, a great increase in vaccinations against SARS-CoV-2 occurred after the introduction of Green Pass (26.7% vs 72.9%). The major drivers of flu vaccine skepticism were represented by the feeling of protection regardless of prevention and by concerns regarding vaccines safety and efficacy; conversely compulsory strategies seemed to play a secondary role, since only a minority of the participants identified in the restrictions induced by the certification the major incentive to get immunized against SARS-CoV-2. The focus on this peculiar historical period helps to take a step forward in the comprehension of the complexity and dynamicity of the vaccine hesitancy phenomenon. Future vaccination campaigns will need to consider the role of personal opinions and emotions, interpreted according to the social and political context.

Epidemiological and clinical features of bronchiolitis after the COVID-19 outbreak: comparison of two epidemic seasons.

The first aim of this study was to compare Pediatric Emergency Department (PED) admissions for acute bronchiolitis during the 2022-2023 season to those of the season 2021-2022. The secondary aim was to assess the difference in the recurrence of bronchiolitis episodes in the same patient between the two seasons. This is a retrospective, observational, cross-sectional study conducted at the PED of IRCCS A. Gemelli University Polyclinic Foundation (Rome, Italy). We included all children aged between 0 and 2 years admitted to PED with the diagnosis of bronchiolitis. We compared features of seasons 2021-2022 and 2022-2023. The median age of children enrolled during the 2022-23 season was 5 months (IQR: 2-8) compared to 7 months (IQR: 2-14) in the previous one (P=0.02). We observed in the last season a higher number of children admitted to PED with a high priority code and an increased therapeutic use of high-flow nasal cannula and inhaled adrenaline. During the 2022-23 season we found 31 (12.8%) children presenting more than one episode of bronchiolitis in the same epidemic season, compared to 16 (7.6%) children in the previous season (P=0.048). Our data emphasize that the epidemiological features of bronchiolitis after COVID-19 outbreak have changed and are still evolving.

Nirsevimab immunization's real-world effectiveness in preventing severe bronchiolitis: A test-negative case-control study.

Several clinical trials have shown that nirsevimab, an antibody targeting the respiratory syncytial virus (RSV), reduces RSV bronchiolitis requiring admission. In 2023-2024, Catalonia and Andorra adopted immunization strategies for children <6 months and those born during the epidemic season. This study evaluates the effectiveness of nirsevimab in preventing hospitalizations from RSV bronchiolitis. In the epidemic season of 2023-2024, a test-negative case-control study was conducted in three hospitals from Catalonia and Andorra. Patients <12 months old admitted with bronchiolitis and tested for RSV using molecular microbiology tests were included. The effectiveness in preventing RSV bronchiolitis hospitalization and severe disease was estimated using multivariate models. Comparisons between immunized, non-immunized, and non-eligible patients were made in prospectively collected epidemiological, clinical, and microbiological variables. Two hundred thirty-four patients were included. RSV was detected in 141/234 (60.2%), being less common in the immunized group (37% vs 75%, p < .001). The rate of immunized patients among those eligible was 59.7%. The estimated effectiveness for RSV-associated lower respiratory tract infection was 81.0% (95% confidence interval: 60.9-90.7), and for preventing severe disease (the need for NIV/CMV), 85.6% (41.7-96.4%). No significant differences by immunization status were observed in patients with RSV concerning viral coinfections, the need for NIV/CMV or length of hospital stay. This study provides real-world evidence of the effectiveness of nirsevimab in preventing RSV-lower respiratory tract infection hospitalization and severe disease in infants during their first RSV season following a systematic immunization program. Immunized patients did not exhibit a higher rate of viral coinfections nor differences in clinical severity once admitted.

Timing patterns of initial respiratory syncytial virus infection and factors influencing disease severity in hospitalized infants with different health status.

This study aimed to determine the timing patterns of the initial respiratory syncytial virus (RSV) infection and to identify the factors influencing disease severity in infants of varying health status. A retrospective study was conducted at the Affiliated Children's Hospital of Chongqing Medical University from 2012 to 2022. The timing of the first RSV infection was estimated in infants with differing health status using correlation analysis, considering their birth time. Logistic regression was utilized to identify factors influencing severe RSV infection in these infants.RSV detection primarily occurred in the winter and spring. Epidemic season and peak timing of RSV were not significantly affected by health status or the COVID-19 pandemic. A strong positive correlation was observed between the age at RSV infection and the interval from birth to the RSV peak season. Infants born during the RSV epidemic season exhibited a higher likelihood of infection within the first 2 months postbirth. In contrast, those born outside the RSV epidemic season were more susceptible to infection during the subsequent peak. Notably, infants with pre-existing health conditions contracted RSV at an earlier age compared to their healthy counterparts. Among healthy infants, severe RSV infection was associated with sex, age, and timing of infection. For infants with underlying conditions, severe RSV infection was primarily related to age and timing of infection. The initial timing of RSV infection in infants varied depending on their health status. Young age and infection timing during the RSV epidemic season were significant risk factors for severe RSV infection. These findings provide a theoretical basis for optimizing immunization strategies for infants with diverse health conditions.

Mycoplasma pneumoniae detections in children with lower respiratory infection before and during the COVID-19 pandemic: a large sample study in China from 2019 to 2022

BackgroundNonpharmaceutical interventions (NPIs) implemented to reduce the transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have suppressed the spread of other respiratory viruses during the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to explore the epidemiological trends and clinical characteristics of Mycoplasma pneumoniae (MP) infection among inpatient children with lower respiratory tract infection (LRTI) before and during the COVID-19 pandemic, and investigate the long-term effects of China’s NPIs against COVID-19 on the epidemiology of MP among inpatient children with LRTI.MethodsChildren hospitalised for LRTI at the Department of Pulmonology, The Children’s Hospital, Zhejiang University School of Medicine (Hangzhou, China) between January 2019 and December 2022 were tested for common respiratory pathogens, including Mycoplasma pneumoniae (MP), Chlamydia trachomatis (CT) and other bacteria. Clinical data on age, sex, season of onset, disease spectrum, and combined infection in children with MP-induced LRTI in the past 4 years were collected and analysed.ResultsOverall, 15909 patients were enrolled, and MP-positive cases were 1971 (34.0%), 73 (2.4%), 176 (5.8%), and 952 (20.6%) in 2019, 2020, 2021, and 2022, respectively, with a significant statistical difference in the MP-positive rate over the 4 years (p <0.001). The median age of these children was preschool age (3–6 years), except for 2022, when they were school age (7–12 years), with statistical differences. Comparing the positive rates of different age groups, the school-age children (7–12 years) had the highest positive rate, followed by the preschoolers (3–6 years) in each of the 4 years. Compared among different seasons, the positive rate of MP in children with LRTI was higher in summer and autumn, whereas in 2020, it was highest in spring. The monthly positive rate peaked in July 2019, remained low from 2020 to 2021, and rebounded until 2022. Regarding the disease spectrum, severe pneumonia accounted for the highest proportion (46.3%) pre-pandemic and lowest (0%) in 2020.ConclusionTrends in MP detection in children with LRTIs suggest a possible correlation between COVID-19 NPIs and significantly reduced detection rates. The positivity rate of MP gradually rose after 2 years. The epidemic season showed some differences, but school-age children were more susceptible to MP before and during the COVID-19 pandemic.

Burden of respiratory syncytial virus, human metapneumovirus and influenza virus infections in Japanese adults in the Hospitalized Acute Respiratory Tract Infection study

BackgroundRespiratory syncytial virus (RSV), human metapneumovirus (hMPV), and influenza virus are responsible for acute respiratory tract infections (ARTIs) in adults. We assessed the clinical burden of RSV, hMPV and influenza virus infection among Japanese adults hospitalized with ARTIs. MethodsThe Hospitalized Acute Respiratory Tract Infection (HARTI) study was a multinational, prospective cohort study in adults with ARTIs across the 2017–2019 epidemic seasons. Enrolment in Japan began in Sept 2018 and ran until Oct 2019. The clinical diagnosis of ARTI and the decision to hospitalize the patient were made according to local standard of care practices. Viral testing was performed by reverse transcription polymerase chain reaction. ResultsOf the 173 adults hospitalized with ARTI during this period at the Japan sites, 7 (4.0%), 9 (5.2%), and 11 (6.4%) were positive for influenza virus, RSV, and hMPV, respectively. RSV season was observed from Oct 2018 to Jan 2019, followed by influenza from Dec 2018 to Apr 2019. hMPV was detected across both the RSV and influenza seasons. Two patients with RSV and 1 patient with hMPV required ICU admission whereas none with influenza. Use of antibiotics, bronchodilators and inhaled corticosteroids was high amongst patients with RSV and hMPV at 1, 2, and 3 months’ post-discharge compared with patients with influenza, with few exceptions. ConclusionThese findings highlight the need for a high degree of clinical suspicion for RSV and hMPV infection in adults hospitalized with ARTIs.

Polyanhydride nanovaccine against H3N2 influenza A virus generates mucosal resident and systemic immunity promoting protection

Influenza A virus (IAV) causes significant morbidity and mortality worldwide due to seasonal epidemics and periodic pandemics. The antigenic drift/shift of IAV continually gives rise to new strains and subtypes, aiding IAV in circumventing previously established immunity. As a result, there has been substantial interest in developing a broadly protective IAV vaccine that induces, durable immunity against multiple IAVs. Previously, a polyanhydride nanoparticle-based vaccine or nanovaccine (IAV-nanovax) encapsulating H1N1 IAV antigens was reported, which induced pulmonary B and T cell immunity and resulted in cross-strain protection against IAV. A key feature of IAV-nanovax is its ability to easily incorporate diverse proteins/payloads, potentially increasing its ability to provide broad protection against IAV and/or other pathogens. Due to human susceptibility to both H1N1 and H3N2 IAV, several H3N2 nanovaccines were formulated herein with multiple IAV antigens to examine the “plug-and-play” nature of the polyanhydride nanovaccine platform and determine their ability to induce humoral and cellular immunity and broad-based protection similar to IAV-nanovax. The H3N2-based IAV nanovaccine formulations induced systemic and mucosal B cell responses which were associated with antigen-specific antibodies. Additionally, systemic and lung-tissue resident CD4 and CD8 T cell responses were enhanced post-vaccination. These immune responses corresponded with protection against both homologous and heterosubtypic IAV infection. Overall, these results demonstrate the plug-and-play nature of the polyanhydride nanovaccine platform and its ability to generate immunity and protection against IAV utilizing diverse antigenic payloads.