Interactions between SARS-CoV-2 and influenza, and the impact of coinfection on disease severity: a test-negative design

Influenza vaccine effectiveness against medically-attended influenza infection in 2023/24 season in Hangzhou, China

From 2020, influenza viruses circulation was largely affected by the global coronavirus disease (COVID-19) pandemic, notably leading to the extinction of the B/Yamagata lineage and raising questions about the relevance of the quadrivalent influenza vaccine, which includes this lineage. Evaluating vaccine effectiveness (VE) against influenza infections is important to inform future vaccine programs. A test-negative case-control study was conducted in five tertiary hospitals in Hangzhou, the capital city of Zhejiang province, China, enrolling medically-attended patients aged >6 months who presented with influenza-like illness (ILI) from October 1, 2023, to March 31, 2024. The VE was estimated using multivariate logistic regression models adjusted for sex, age, influenza detection methods, and influenza testing timing. Of the 157,291 medically-attended ILI participants enrolled 56,704 (36%) tested positive for influenza. Adjusted overall VE against any medically-attended influenza infection was 48% (95% Confidence interval [CI]: 46%-51%). The overall VE of the trivalent inactivated influenza vaccine (IIV3) was 59% (95% CI: 50%-66%), followed by the trivalent live attenuated vaccine (LAIV3) (VE = 53%, 95% CI: 42%-62%) and quadrivalent inactivated influenza vaccine (IIV4) (VE = 47%, 95% CI: 45%-50%). IIV3 provided even better protection against medically-attended influenza B infection than IIV4 (VE = 87%, 95% CI: 81%-92% for IIV3 versus VE = 53%, 95% CI: 50%-57% for IIV4). In the 2023/24 season in Hangzhou, China, the influenza vaccine offered moderate protection during a major epidemic. The results supported the World Health Organization recommendation to exclude the B/Yamagata lineage antigen in quadrivalent influenza vaccines in 2023.

Determinants of seasonal influenza vaccination uptake, intention and recommendations among Lebanese physicians

The most effective way to prevent influenza infection and its severe outcomes is through vaccination. Influenza vaccination is recommended for high-risk groups, including health care workers who have high occupational exposure. Hesitancy is a major challenge affecting vaccine uptake. This study aims to identify the determinants of seasonal influenza vaccine uptake, intention and recommendation to target groups of physicians in Lebanon. A cross-sectional study was conducted targeting physicians working in Lebanon. Data was collected on Kobo Toolbox using an online questionnaire developed based on the Health Belief Model. A random sample of physicians was selected from the Order of Physicians database. The link to the questionnaire was sent by email or message. Univariate, bivariate and multivariable analyses were performed using R software. The total number of responses was 1019. Half (49 %) of the participants received the vaccine in the 2022-2023 season, and 73 % intend to get it if recommended and offered for free. The perception of vaccine effectiveness was associated with vaccine uptake (adjusted OR = 2.54, 95 %CI = 1.98-3.31), intention to be vaccinated (adjusted OR = 17.5, 95 %CI = 7.21-50.5) and vaccine recommendation. Perception of vaccine safety, type of healthcare facility and physician's specialty were also associated with flu uptake. Other predictors for intention were: perception of disease severity and flu uptake during the previous season. Other predictors for flu vaccine recommendation were: province of residence, number of years in healthcare, specialty and intention to take the flu vaccine (adjusted OR = 21.0, 95 %CI = 7.58-71.3). Influenza vaccine uptake among participating physicians is suboptimal, yet intention to take the vaccine is higher. The study identified several factors associated with the vaccine uptake, intention and recommendation. A multifaceted approach and targeted education activities are needed in a sustainable vaccination program to increase physicians' influenza vaccine uptake.

Year-round infectome profiling of acute febrile respiratory illness unveiled complex epidemiological dynamics post-lifting of COVID-19 restrictions

OBJECTIVES

Following the lifting of COVID-19 non-pharmaceutical interventions in China, respiratory infections surged, though the specific causes remained unclear. This study provided a comprehensive overview of the infectome in patients with acute febrile respiratory illness (AFRI) to inform disease surveillance.

METHODS

Between March 2023 and February 2024, 1,163 oropharyngeal swabs from AFRI patients and 338 from healthy individuals were collected in Shenzhen. Meta-transcriptomic sequencing was employed for microbial analysis.

RESULTS

We identified 14 viruses and 10 bacteria species known to cause human disease. Influenza virus, SARS-CoV-2, Streptococcus pneumoniae, and redondovirus were the most common, with a negative correlation between H3N2 and SARS-CoV-2. Notably, we detected certain enterovirus subtypes (e.g., Coxsackievirus A6 and Echovirus 30), previously overlooked pathogens (e.g., redondovirus), and rare pathogens like Streptococcus pseudopneumoniae. Comparisons revealed five pathogens showed significantly higher abundance in patients than in controls, despite no significant differences for others probably due to their limited number of positive pools. Seasonal shifts in microbial diversity and composition were observed, with climate factors like temperature and precipitation playing a role. Phylogenetic analysis revealed changes in genotype diversity and dominant pathogen lineages.

CONCLUSIONS

This study highlighted complex pathogen infections in AFRI patients following COVID-19 restrictions, demonstrating the value of meta-transcriptomics over PCR-based methods for more detailed pathogen surveillance.

Changes in Seasonal Patterns for Common Pediatric Respiratory Viruses During the COVID Pandemic

OBJECTIVES

Observed alterations in seasonal patterns of common pediatric respiratory viruses during and immediately after the COVID-19 pandemic had far-reaching implications for the care of ill children. Here, we quantify the effects of the pandemic and related nonpharmaceutical interventions on the prevalence and seasonality of common pediatric respiratory illnesses.

METHODS

We performed a retrospective chart review within a large health network to identify incidence rates of common respiratory viruses and compared them to historical trends. Time series analyses using seasonal autoregressive integrated moving average models were utilized to identify seasonal patterns for the different virus types and quantify deviations from expected incidence rates.

RESULTS

Overall, we noted a steep decline in non-COVID viral infection rates at the onset of the COVID pandemic in March 2020, largely coincident with the institution of mask mandates and lockdown measures. This trend continued until the Spring of 2021, at which time non-COVID infections resurged to rates higher than pre-COVID levels. In addition, the historically observed seasonality of these viruses was significantly disrupted by the pandemic. In particular, the historical peaks for influenza A and human metapneumovirus shifted from February and March, respectively, to bimodal peaks in December 2021 and May 2022; respiratory syncytial virus demonstrated an unprecedented Spring/Summer season in 2021; parainfluenza type 1 was unusually active in 2022, an even-numbered year; and influenza B virtually disappeared during and immediately after the pandemic.

CONCLUSIONS

Our observations add to the growing body of literature supporting the hypothesis that human interactions are one of the key drivers of pediatric respiratory viral seasonality in addition to climate. Understanding the effect of human interactions on disease spread is crucial for the development of effective mitigation measures for future pandemics while avoiding dangerous spikes of other illnesses once those interventions are lifted.

Global analysis of influenza epidemic characteristics in the first two seasons after lifting the nonpharmaceutical interventions for COVID-19

OBJECTIVES

The COVID-19 pandemic significantly disrupted the global influenza seasonal patterns due to nonpharmaceutical interventions. This study aims to describe the influenza seasonal characteristics in the first two seasons after lifting COVID-19 NPIs and assess shifts before, during, and after the pandemic.

METHODS

We analyzed country-specific weekly influenza data (2011-2024) from WHO FluNet and collected COVID-19 NPI timing from official announcements. The study was divided into pre-pandemic, pandemic, and post-pandemic phases, estimating epidemic onset, peak week, peak intensity, and duration by climate zones.

RESULTS

In temperate countries, peak intensity after the pandemic decreased by 8.4 %, while duration increased by 1.8 weeks, and onset and peak were delayed by 18.5 and 22.8 weeks compared to regular seasonal pattern before the pandemic. Subtropical countries experienced a 17.2 % decrease in peak intensity, a 2.4-week decrease in duration, and delays in onset and peak by 13.5 and 2.3 weeks. Tropical countries had a 10 % decrease in peak intensity, a 3-week reduction in duration, and a 6.6-week delay in onset with no significant change in peak time.

CONCLUSION

Influenza seasonality shifted significantly after the pandemic, with epidemic durations returning to typical patterns but peak intensities remained low. Robust surveillance after an infectious disease pandemic is crucial to inform prevention and control strategies.

Differences in clinical characteristics between coronavirus disease 2019 (COVID-19) and influenza: a systematic review and meta-analysis

The coronavirus disease 2019 (COVID-19) epidemic has brought major challenges to the global health system, and influenza is also a problem that cannot be ignored. We aimed to explore and compare the clinical characteristics of COVID-19 and influenza to deepen the understanding of these two diseases and provide some guidance for clinicians to make differential diagnoses. We searched PubMed, Embase and Web of Science for articles and performed a meta-analysis using Stata 14.0 with a random-effects model. This meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. One hundred articles involving 226,913 COVID-19 patients and 201,617 influenza patients were included, and all the articles included patients with these two diseases as experimental and control groups. Compared to influenza, COVID-19 was more common among men (OR = 1.46, 95% CI: 1.23-1.74) and people with a higher body mass index (MD = 1.43, 95% CI: 1.09-1.77). The proportion of current smokers among COVID-19 patients was lower than that among influenza patients (OR = 0.25, 95% CI: 0.18-0.33). Patients with COVID-19 had longer stays in the hospital (MD = 3.20, 95% CI: 2.58-3.82) and ICU (MD = 3.10, 95% CI: 1.44-4.76), required mechanical ventilation more frequently (OR = 2.30, 95% CI: 1.77-3.00), and had higher mortality (OR = 2.22, 95% CI: 1.93-2.55). We also found significant differences in some blood parameters between the two groups of patients. Upper respiratory symptoms were more obvious in influenza patients, and the proportion of comorbidities was higher than that among COVID-19 patients. There are some differences in the major characteristics, symptoms, laboratory findings and comorbidities between COVID-19 patients and influenza patients. COVID-19 patients often require more medical resources and have worse clinical outcomes.

Respiratory Pathogen Profiles of Patients - Beijing Municipality, China, November 2023-April 2024

Introduction

Respiratory pathogens pose a complex challenge for public health systems. In the winter of 2023, multiple respiratory pathogens showed staggered epidemic waves. Additionally, co-infections involving various pathogens were observed, resulting in significant disease burdens. Understanding the epidemiological dynamics of these pathogens is essential for supporting public health systems in the prevention and control of respiratory infectious diseases.

Methods

Respiratory samples were collected from patients in Beijing presenting with influenza-like symptoms to detect 27 respiratory pathogens using multiplex qPCR.

Results

Four distinct epidemic waves were identified. The first wave was a pre-winter outbreak of Mycoplasma pneumoniae (M. pneumoniae). This was then followed by successive waves of influenza A and B viruses. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exhibited a resurgence by the end of February 2024. Age-dependent susceptibility varied, with SARS-CoV-2 and influenza A/B peaking in the 30-40-year age group. Conversely, adenovirus, rhinovirus, M. pneumoniae, Moraxella catarrhalis (M. catarrhalis), and Haemophilus influenzae (H. influenzae) were more common in adolescents and the elderly. Furthermore, 18.8% of cases were identified as co-infections with more than two pathogens. H. influenzae was found to frequently co-infect with viral and bacterial pathogens.

Conclusions

Respiratory pathogens exhibited different prevalence trends during the first influenza season following the COVID-19 pandemic. Influenza viruses showed a higher peak incidence and delayed seasonality. Moreover, the co-circulation of viral and bacterial infections increased the complexity of respiratory infections. Interestingly, staggered epidemic waves between SARS-CoV-2 and influenza A/B viruses were observed. Consequently, SARS-CoV-2 may become a seasonal virus, causing epidemics alongside influenza viruses. However, further research is needed to elucidate its epidemiological patterns. The co-circulation of these epidemic viruses and other respiratory pathogens underscores the need for enhanced diagnostic and intervention strategies, including vaccination campaigns.

Lethal Synergistic Infections by Two Concurrent Respiratory Pathogens

Lethal synergistic infections by concurrent pathogens have occurred in humans, including human immunodeficiency virus and Mycobacterium tuberculosis infections, or in animal or human models of influenza virus, or bacteria, e.g., Streptococcus pneumoniae, concurrent with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, the intracellular synergistic interaction possibilities between two respiratory viral pathogens, or between viral and fungal pathogens, merits additional examination. The requirements for synergistic concurrent pathogen infections are: a) relatively little detrimental interference between two pathogens, b) one pathogen having the capability of directly or indirectly assisting the second pathogen by direct immuno-manipulation or indirect provision of infection opportunities and/or metabolic assistance, c) substantial human or environmental prevalence, possibly including a prevalence in any type of health-care facilities or other locations having congregations of potentially infected human or animal vectors and d) substantial transmissibility of the pathogens, which would make their concurrent pathogen infections much more probable. A new definition of pathogen synergy is proposed: "pathogen synergy is an interaction of two or more pathogens during concurrent infections causing an increased infection severity compared to mono-infections by the individual pathogens." Non-respiratory pathogens can also concurrently infect organs besides the lungs. However, the air-transmissible respiratory pathogens, particularly the RNA viruses, can enable highly widespread and synergistic concurrent infections. For instance, certain strains of coronaviruses, influenza viruses and similar respiratory viruses, are highly transmissible and/or widely prevalent in various vectors for transmission to humans and have numerous capabilities for altering lung immune defenses.

Association between combination COVID-19-influenza vaccination and long COVID in middle-aged and older Europeans: A cross-sectional study

The potential impact of combined COVID-19 and influenza vaccination on long COVID remains uncertain. In the present cross-sectional study, we aimed to investigate the plausible association between them in middle-aged and older Europeans based on the Survey of Health, Ageing, and Retirement in Europe (SHARE). A total of 1910 participants were recruited in the analyses. The study outcome was long COVID. Participants were divided into 4 groups through the self-reported status of COVID-19 and influenza vaccination. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated. 1397 participants experienced long COVID. After multivariable adjustment, those vaccinated with neither COVID-19 nor influenza vaccine had higher risk of long COVID (OR, 1.72; 95% CI, 1.26-2.35) compared to those vaccinated with both vaccines. Furthermore, adding the 4 statuses of COVID-19 vaccination/influenza vaccination to conventional risk model improved risk reclassification for long COVID (continuous net reclassification improvement was 16.26% [p = .003], and integrated discrimination improvement was 0.51% [p = .005]). No heterogeneity was found in the subgroup analyses (all p-interaction ≥0.05). Our study might provide a strategy for people aged 50 and over to reduce the occurrence of long COVID, that is, to combine the use of the COVID-19 vaccine and influenza vaccines.

Seasonal Shifts in Influenza, Respiratory Syncytial Virus, and Other Respiratory Viruses After the COVID-19 Pandemic: An Eight-Year Retrospective Study in Jalisco, Mexico

The coronavirus disease 2019 (COVID-19) pandemic profoundly disrupted the epidemiology of respiratory viruses, driven primarily by widespread non-pharmaceutical interventions (NPIs) such as social distancing and masking. This eight-year retrospective study examines the seasonal patterns and incidence of influenza virus, respiratory syncytial virus (RSV), and other respiratory viruses across pre-pandemic, pandemic, and post-pandemic phases in Jalisco, Mexico. Weekly case counts were analyzed using an interrupted time series (ITS) model, segmenting the timeline into these three distinct phases. Significant reductions in respiratory virus circulation were observed during the pandemic, followed by atypical resurgences as NPIs were relaxed. Influenza displayed alternating subtype dominance, with influenza A H3 prevailing in 2022, influenza B surging in 2023, and influenza A H1N1 increasing thereafter, reflecting potential immunity gaps. RSV activity was marked by earlier onset and higher intensity post-pandemic. Other viruses, including human rhinovirus/enterovirus (HRV/HEV) and parainfluenza virus (HPIV), showed altered dynamics, with some failing to return to pre-pandemic seasonality. These findings underscore the need for adaptive surveillance systems and vaccination strategies to address evolving viral patterns. Future research should investigate the long-term public health implications, focusing on vaccination, clinical outcomes, and healthcare preparedness.

Comparison of clinical and laboratory characteristics of COVID-19 and influenza in hospitalized children

PURPOSE

COVID-19 and influenza infections have similar modes of transmission and clinical symptoms but have different prognoses and treatment methods; therefore, it is important to make a final diagnosis. Herein, we aimed to compare the demographic, clinical, and laboratory differences in hospitalized pediatric patients with COVID-19 and influenza.

METHODS

This retrospective study comprised patients with COVID-19 managed between March 2020 to February 2022, and patients with influenza managed between December 2017 to February 2022, at a tertiary care hospital. The clinical data and laboratory parameters were obtained from the medical records of the hospital. Pediatric intensive care unit (PICU) admission, need for oxygen support, and the mortality rates of the patients were recorded and compared statistically.

RESULTS

Overall, 107 patients with COVID-19 and 250 patients with influenza were included. Underlying chronic disease (UCD) rates were statistically higher in patients with COVID-19 (p < 0.001). When the symptoms were compared, fever, cough, and runny nose were more common in patients with influenza, and abdominal pain and rash were more common in patients with COVID-19 (p < 0.05). In patients with influenza, white blood cell count and absolute neutrophil count values were lower (p = 0.021 and p = 0.037, respectively), and aspartate aminotransferase and creatinine kinase values were higher (p = 0.007 and p < 0.001, respectively). PICU admission rates and oxygen support needs were similar in both groups (p > 0.05). When the virus was COVID-19, it had 7.8 times higher risk of mortality compared to influenza (p = 0.002). There were statistically significant risk for mortality when the virus was COVID-19, the risk of mortality was 6.9 times higher in those with UCD, 8.5 times higher in those with admission to PICU and 3.8 times higher in those with needing mechanical ventilation (MV) compared to when the virus was influenza (p = 0.004, p = 0.006 and p = 0.049, respectively). The mortality rate was higher in patients with COVID-19 (p = 0.007).

CONCLUSION

This study showed that COVID-19 might negatively affect the survival times and increase mortality rates, especially in children with an UCD, admitted to the PICU and in need of MV.

Circulation and Codetections of Influenza Virus, SARS-CoV-2, Respiratory Syncytial Virus, Rhinovirus, Adenovirus, Bocavirus, and Other Respiratory Viruses During 2022-2023 Season in Latvia

This retrospective study analysed the routine data obtained by multiplex real-time RT-qPCR methods for respiratory virus detection. A total of 4814 respiratory specimens collected during 1 September 2022-31 August 2023 were included in the study. A total of 38% of the specimens were positive for at least one target, with the incidence maximum (82%) for the small children (age group 0-4 years). The five dominant virus groups were rhinovirus (RV, 12%), influenza virus A (IAV, 7%), adenovirus (AdV, 6%), respiratory syncytial virus (RSV, 5%), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, 5%). The specimens with multi-detections represented 19% of the positives, unevenly distributed (n = 225, 56, 43, 24) among the age groups 0-4, 5-14, 15-64, and 65< years, respectively. The dominant virus groups in multi-positive specimens were RV (53%), AdV (43%), and bocavirus (BoV, 35%)-in mutual pairs as well as all three together-followed by RSV (21%), and IAV (15%). Our study focused on the specimens with codetections and provides an insight into the variety of the respiratory virus interactions in Latvia during the first year since pandemic-related social restriction measures were eased. The observations also emphasise the need to consider the differentiation between rhinoviruses and enteroviruses, especially for the youngest patients in the age group 0-4.

Co-infection of SARS-CoV-2 and Influenza A: a report from in Southwestern Iran

Background

Since December 2019, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) started in China, and quickly spread worldwide. To date, SARS-CoV-2 infection has become a global concern and health problem.

Method

In this study, we evaluated the co-infection of SARS-CoV-2 and Influenza viruses in confirmed COVID-19 patients in Abadan, Iran. They referred to the centers for COVID-19 detection at Abadan University of Medical Sciences in Southwest Iran. Nasopharyngeal and oropharyngeal throat swabs were collected from each person and tested for Influenza A using a multiplex Real Time-Polymerase Chain Reaction.

Results

In this study, among 40 SARS-CoV-2-positive cases, 2 patients (5%) were co-infected with influenza A virus.

Conclusion

The low frequency of influenza in our study could be due to the small sample size, which is one of the main limitations of our study Also, other respiratory tract infections were not investigated in this study.

Prospective cohort study of patient demographics, viral agents, seasonality, and outcomes of influenza-like illness in Mexico in the late H1N1-pandemic and post-pandemic years (2010-2014)

Objectives

Influenza-like illness (ILI) caused by respiratory viruses results in various respiratory clinical manifestations. The ILI002 prospective observational cohort study aimed to describe viral agents, seasonality, and outcomes of patients with ILI during four seasons in the influenza H1N1-pandemic and post-pandemic years (2010-2014).

Methods

Patients from six Mexican hospitals were enrolled from April 2010 to March 2014. Clinical data and nasopharyngeal swabs were obtained and tested for viral respiratory pathogens by real-time reverse-transcription polymerase chain reaction.

Results

Of the 5662 enrolled participants, 64.9% were adults and 35.1% were children. Among the 5629 participants with single-pathogen detection, rhinovirus (20.2%), influenza virus (11.2%), respiratory syncytial virus (RSV) (7.2%), and coronavirus (6.8%) were the most frequent pathogens. Co-infection occurred in 14.5% of cases; 49.3% of participants required hospitalization, particularly in RSV cases (42.9% adults, 89.6% children). The mortality rate was 2.8% higher among older adult participants and those with comorbidities. Influenza H1N1 had the highest mortality rate, yet almost half of the deceased had no pathogen. Rhinovirus persisted year-round, while influenza, coronavirus, and RSV peaked during cooler months.

Conclusions

Analyses showed that some viruses causing ILI may lead to severe disease and hospitalization irrespective of comorbidities. These findings may help in decision-making about public health policies on prevention measures, vaccination, treatment, and administration of health care.

Infection Rates and Symptomatic Proportion of SARS-CoV-2 and Influenza in Pediatric Population, China, 2023

We conducted a longitudinal cohort study of SARS-CoV-2 and influenza rates in childcare centers and schools in Wuxi, China, collecting 1,760 environmental samples and 9,214 throat swabs from 593 students (regardless of symptoms) in weekly collections during February-June 2023. We estimated a cumulative infection rate of 124.8 (74 episodes)/1,000 persons for SARS-CoV-2 and 128.2 (76 episodes)/1,000 persons for influenza. The highest SARS-CoV-2 infection rate was in persons 18 years of age, and for influenza, in children 4 years of age. The asymptomatic proportion of SARS-CoV-2 was 59.6% and 66.7% for influenza; SARS-CoV-2 symptomatic proportion was lower in 16-18-year-olds than in 4-6-year-olds. Only samples from frequently touched surface tested positive for SARS-CoV-2 (4/1,052) and influenza (1/1,052). We found asynchronous circulation patterns of SARS-CoV-2 and influenza, similar to trends in national sentinel surveillance. The results support vaccination among pediatric populations and other interventions, such as environmental disinfection in educational settings.

Combating the Co-Circulation of SARS-CoV-2 and Seasonal Influenza: Identifying Multi-Dimensional Factors Associated with the Uptake of Seasonal Influenza Vaccine among a Chinese National Sample

INTRODUCTION

The co-circulation of COVID-19 and seasonal influenza highlighted the importance of promoting influenza vaccination. However, the influenza vaccination rate among the Chinese population is low and requires further promotion. This study examined multi-dimensional factors, such as knowledge of seasonal influenza, health perceptions, cues to action, patient-provider relationships, and COVID-19 pandemic-related factors, in relation to the uptake of the seasonal influenza vaccine (SIV) among the Chinese population.

METHODS

A cross-sectional, self-administered online survey using a quota sampling method was conducted among Chinese adults 18 years and older between June and August 2022. Multivariate logistic regression was performed to explore factors associated with the 2021 SIV behavior.

RESULTS

A total of 3161 individuals from different regions of China were included in this study. The multivariate logistic regression demonstrated that perceived severity of influenza, perceived barriers to taking SIV, cues to action, a stable relationship with providers, worry about contracting COVID-19 in immunization settings, non-pharmaceutical interventions (NPIs), and awareness of the influenza vaccine in protecting against COVID-19 were significantly associated with the SIV uptake.

CONCLUSIONS

This study examined multi-dimensional factors that may influence SIV uptake. Health promotion programs should incorporate multi-dimensional factors, including personal and environmental factors, related to SIV promotion during the co-circulation period.

Cause-specific excess mortality in Denmark, Finland, Norway, and Sweden during the COVID-19 pandemic 2020-2022: a study using nationwide population data

While there is substantial evidence on excess mortality in the first two years of the COVID-19 pandemic, no study has conducted a cause-specific analysis of excess mortality for the whole period 2020-2022 across multiple countries. We examined cause-specific excess mortality during 2020-2022 in Denmark, Finland, Norway, and Sweden-four countries with similar demographics and welfare provisions, which implemented different pandemic response policies. To this end, we utilized nationwide register-based information on annual cause-specific deaths stratified by age and sex, and applied linear regression models to predict mortality in 2020-2022 based on the reference period 2010-2019. Excess deaths were obtained by contrasting actual and expected deaths. Additional analyses employed standardization to a common population, as well as population adjustments to account for previous deaths. Our results showed that, besides deaths due to COVID-19 (a total of 32,491 during 2020-2022), all countries experienced excess deaths due to cardiovascular diseases (in total 11,610 excess deaths), and under-mortality due to respiratory diseases other than COVID-19 (in total 9878) and dementia (in total 8721). The excess mortality due to cardiovascular diseases was particularly pronounced in Finland and Norway in 2022, and the under-mortality due to dementia was particularly pronounced in Sweden in 2021-2022. In conclusion, while COVID-19 deaths emerge as the most apparent consequence of the pandemic, our findings suggest that mortality has also been influenced by substitutions between different causes of death and over time, as well as indirect consequences of COVID-19 infection and pandemic responses-albeit to different extents in the different countries.

Impact of the COVID-19 Pandemic on Influenza Hospital Admissions and Deaths in Wales: Descriptive National Time Series Analysis

Background

The COVID-19 pandemic and the ensuing implementation of control measures caused widespread societal disruption. These disruptions may also have affected community transmission and seasonal circulation patterns of endemic respiratory viruses.

Objective

We aimed to investigate the impact of COVID-19-related disruption on influenza-related emergency hospital admissions and deaths in Wales in the first 2 years of the pandemic.

Methods

A descriptive analysis of influenza activity was conducted using anonymized pathology, hospitalization, and mortality data from the Secure Anonymised Information Linkage Databank in Wales. The annual incidence of emergency hospitalizations and deaths with influenza-specific diagnosis codes between January 1, 2015, and December 31, 2021, was estimated. Case definitions of emergency hospitalization and death required laboratory confirmation with a polymerase chain reaction test. Trends of admissions and deaths were analyzed monthly and yearly. We conducted 2 sensitivity analyses by extending case definitions to include acute respiratory illnesses with a positive influenza test and by limiting admissions to those with influenza as the primary diagnosis. We also examined yearly influenza testing trends to understand changes in testing behavior during the pandemic.

Results

We studied a population of 3,235,883 Welsh residents in 2020 with a median age of 42.5 (IQR 22.9-61.0) years. Influenza testing in Wales increased notably in the last 2 months of 2020, and particularly in 2021 to 39,720 per 100,000 people, compared to the prepandemic levels (1343 in 2019). The percentage of influenza admissions matched to an influenza polymerase chain reaction test increased from 74.8% (1890/2526) in 2019 to 85.2% (98/115) in 2021. However, admissions with a positive test per 100,000 population decreased from 17.0 in 2019 to 2.7 and 0.6 in 2020 and 2021, respectively. Similarly, deaths due to influenza with a positive influenza test per 100,000 population decreased from 0.4 in 2019 to 0.0 in 2020 and 2021. Sensitivity analyses showed similar patterns of decreasing influenza admissions and deaths in the first 2 years of the COVID-19 pandemic.

Conclusions

Nonpharmaceutical interventions to control COVID-19 were associated with a substantial reduction in the transmission of the influenza virus, with associated substantial reductions in hospital cases and deaths observed. Beyond the pandemic context, consideration should be given to the role of nonpharmaceutical community-driven interventions to reduce the burden of influenza.

Clinical Evaluation of the Accuracy of the Panbio™ COVID-19/Flu A&B Rapid Panel: A Combination Antigen Rapid Diagnostic Test for the Omicron Variant and Influenza A Virus

It is difficult to differentiate between coronavirus disease 2019 (COVID-19) and influenza based on the symptoms. In the present study, a newly developed antigen rapid diagnostic test (Ag-RDT) called Panbio™ COVID-19/Flu A&B that can simultaneously detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A/B virus was evaluated. Its accuracy was evaluated using 235 pairs of nasopharyngeal samples collected from patients with respiratory symptoms and fever (>37.5°C). Reverse transcription polymerase chain reaction was used as a reference method to evaluate the accuracy of the SARS-CoV-2 detection. We confirmed the accuracy of the developed Ag-RDT against the Omicron variant where the sensitivity and specificity were 94.8% and 100%, respectively. In addition, to identify the influenza A virus, a noninferiority test was conducted using a commercial Ag-RDT, which has a sensitivity and specificity in comparison with viral culture of 94.8% and 98.4%, respectively. The positive and negative predictive values for influenza A virus were 98.5% and 98.1%, respectively, for the Panbio COVID-19/Flu A&B test. The evaluation of this newly developed Ag-RDT using clinical samples suggests that it has a high efficacy in clinical settings.

Prevalence and Clinical Impact of Viral and Bacterial Coinfections in Hospitalized Children and Adolescents Aged under 18 Years with COVID-19 during the Omicron Wave in Russia

The COVID-19 pandemic has altered respiratory infection patterns in pediatric populations. The emergence of the SARS-CoV-2 Omicron variant and relaxation of public health measures have increased the likelihood of coinfections. Previous studies show conflicting results regarding the impact of viral and bacterial coinfections with SARS-CoV-2 on severity of pediatric disease. This study investigated the prevalence and clinical impact of coinfections among children hospitalized with COVID-19 during the Omicron wave. A retrospective analysis was conducted on 574 hospitalized patients aged under 18 years in Russia, from January 2022 to March 2023. Samples from patients were tested for SARS-CoV-2 and other respiratory pathogens using qRT-PCR, bacterial culture tests and mass spectrometry, and ELISA. Approximately one-third of COVID-19 cases had coinfections, with viral and bacterial coinfections occurring at similar rates. Adenovirus and Staphylococcus aureus were the most common viral and bacterial coinfections, respectively. Viral coinfections were associated with higher fevers and increased bronchitis, while bacterial coinfections correlated with longer duration of illness and higher pneumonia rates. Non-SARS-CoV-2 respiratory viruses were linked to more severe lower respiratory tract complications than SARS-CoV-2 monoinfection. These findings suggest that during the Omicron wave, seasonal respiratory viruses may have posed a greater threat to children's health than SARS-CoV-2.

Viral interference between severe acute respiratory syndrome coronavirus 2 and influenza A viruses

Some respiratory viruses can cause a viral interference through the activation of the interferon (IFN) pathway that reduces the replication of another virus. Epidemiological studies of coinfections between SARS-CoV-2 and other respiratory viruses have been hampered by non-pharmacological measures applied to mitigate the spread of SARS-CoV-2 during the COVID-19 pandemic. With the ease of these interventions, SARS-CoV-2 and influenza A viruses can now co-circulate. It is thus of prime importance to characterize their interactions. In this work, we investigated viral interference effects between an Omicron variant and a contemporary influenza A/H3N2 strain, in comparison with an ancestral SARS-CoV-2 strain and the 2009 pandemic influenza A/H1N1 virus. We infected nasal human airway epitheliums with SARS-CoV-2 and influenza, either simultaneously or 24 h apart. Viral load was measured by RT-qPCR and IFN-α/β/λ1/λ2 proteins were quantified by immunoassay. Expression of four interferon-stimulated genes (ISGs; OAS1/IFITM3/ISG15/MxA) was also measured by RT-droplet digital PCR. Additionally, susceptibility of each virus to IFN-α/β/λ2 recombinant proteins was determined. Our results showed that influenza A, and especially A/H3N2, interfered with both SARS-CoV-2 viruses, but that SARS-CoV-2 did not significantly interfere with A/H3N2 or A/H1N1. Consistently with these results, influenza, and particularly the A/H3N2 strain, caused a higher production of IFN proteins and expression of ISGs than SARS-CoV-2. SARS-CoV-2 induced a marginal IFN production and reduced the IFN response during coinfections with influenza. All viruses were susceptible to exogenous IFNs, with the ancestral SARS-CoV-2 and Omicron being less susceptible to type I and type III IFNs, respectively. Thus, influenza A causes a viral interference towards SARS-CoV-2 most likely through an IFN response. The opposite is not necessarily true, and a concurrent infection with both viruses leads to a lower IFN response. Taken together, these results help us to understand how SARS-CoV-2 interacts with another major respiratory pathogen.

Interaction and antiviral treatment of coinfection between SARS-CoV-2 and influenza in vitro

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Does Prior Respiratory Viral Infection Provide Cross-Protection Against Subsequent Respiratory Viral Infections? A Systematic Review and Meta-Analysis

The epidemiology of different respiratory viral infections is believed to be affected by prior viral infections in addition to seasonal effects. This PROSPERO-registered systematic review identified 7388 studies, of which six met our criteria to answer the question specifically. The purpose of this review was to compare the prevalence of sequential viral infections in those with previously documented positive versus negative swabs. The pooled prevalence of sequential viral infections over varying periods from 30-1000 days of follow-up was higher following a negative respiratory viral swab at 0.15 than following a positive swab at 0.08, indicating the potential protective effects of prior respiratory viral infections. However, significant heterogeneity and publication biases were noted. There is some evidence, albeit of low quality, of a possible protective effect of an initial viral infection against subsequent infections by a different virus, which is possibly due to broad, nonspecific innate immunity. Future prospective studies are needed to validate our findings.

Towards broad-spectrum protection: the development and challenges of combined respiratory virus vaccines

In the post-COVID-19 era, the co-circulation of respiratory viruses, including influenza, SARS-CoV-2, and respiratory syncytial virus (RSV), continues to have significant health impacts and presents ongoing public health challenges. Vaccination remains the most effective measure for preventing viral infections. To address the concurrent circulation of these respiratory viruses, extensive efforts have been dedicated to the development of combined vaccines. These vaccines utilize a range of platforms, including mRNA-based vaccines, viral vector vaccines, and subunit vaccines, providing opportunities in addressing multiple pathogens at once. This review delves into the major advancements in the field of combined vaccine research, underscoring the strategic use of various platforms to tackle the simultaneous circulation of respiratory viruses effectively.

Coxsackievirus A7 and Enterovirus A71 Significantly Reduce SARS-CoV-2 Infection in Cell and Animal Models

In this study, we investigated the features of co-infection with SARS-CoV-2 and the enterovirus vaccine strain LEV8 of coxsackievirus A7 or enterovirus A71 for Vero E6 cells and Syrian hamsters. The investigation of co-infection with SARS-CoV-2 and LEV-8 or EV-A71 in the cell model showed that a competitive inhibitory effect for these viruses was especially significant against SARS-CoV-2. Pre-infection with enteroviruses in the animals caused more than a 100-fold decrease in the levels of SARS-CoV-2 virus replication in the respiratory tract and more rapid clearance of infectious SARS-CoV-2 from the lower respiratory tract. Co-infection with SARS-CoV-2 and LEV-8 or EV-A71 also reduced the severity of clinical manifestations of the SARS-CoV-2 infection in the animals. Additionally, the histological data illustrated that co-infection with strain LEV8 of coxsackievirus A7 decreased the level of pathological changes induced by SARS-CoV-2 in the lungs. Research into the chemokine/cytokine profile demonstrated that the studied enteroviruses efficiently triggered this part of the antiviral immune response, which is associated with the significant inhibition of SARS-CoV-2 infection. These results demonstrate that there is significant viral interference between the studied strain LEV-8 of coxsackievirus A7 or enterovirus A71 and SARS-CoV-2 in vitro and in vivo.

Sequential Infection with Influenza A Virus Followed by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Leads to More Severe Disease and Encephalitis in a Mouse Model of COVID-19

COVID-19 is a spectrum of clinical symptoms in humans caused by infection with SARS-CoV-2. The coalescence of SARS-CoV-2 with seasonal respiratory viruses, particularly influenza viruses, is a global health concern. To understand this, transgenic mice expressing the human ACE2 receptor (K18-hACE2) were infected with influenza A virus (IAV) followed by SARS-CoV-2 and the host response and effect on virus biology was compared to K18-hACE2 mice infected with IAV or SARS-CoV-2 alone. The sequentially infected mice showed reduced SARS-CoV-2 RNA synthesis, yet exhibited more rapid weight loss, more severe lung damage and a prolongation of the innate response compared to the singly infected or control mice. Sequential infection also exacerbated the extrapulmonary encephalitic manifestations associated with SARS-CoV-2 infection. Conversely, prior infection with a commercially available, multivalent live-attenuated influenza vaccine (Fluenz Tetra) elicited the same reduction in SARS-CoV-2 RNA synthesis, albeit without the associated increase in disease severity. This suggests that the innate immune response stimulated by IAV inhibits SARS-CoV-2. Interestingly, infection with an attenuated, apathogenic influenza vaccine does not result in an aberrant immune response and enhanced disease severity. Taken together, the data suggest coinfection ('twinfection') is deleterious and mitigation steps should be instituted as part of the comprehensive public health and management strategy of COVID-19.

From intramuscular to nasal: unleashing the potential of nasal spray vaccines against coronavirus disease 2019

Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected 700 million people worldwide since its outbreak in 2019. The current pandemic strains, including Omicron and its large subvariant series, exhibit strong transmission and stealth. After entering the human body, the virus first infects nasal epithelial cells and invades host cells through the angiotensin-converting enzyme 2 receptor and transmembrane serine protease 2 on the host cell surface. The nasal cavity is an important body part that protects against the virus. Immunisation of the nasal mucosa produces immunoglobulin A antibodies that effectively neutralise viruses. Saline nasal irrigation, a type of physical therapy, can reduce the viral load in the nasal cavity and prevent viral infections to some extent. As a commonly used means to fight SARS-CoV-2, the intramuscular (IM) vaccine can induce the human body to produce a systemic immune response and immunoglobulin G antibody; however, the antibody is difficult to distribute to the nasal mucosa in time and cannot achieve a good preventive effect. Intranasal (IN) vaccines compensate for the shortcomings of IM vaccines, induce mucosal immune responses, and have a better effect in preventing infection. In this review, we discuss the nasal defence barrier, the harm caused by SARS-CoV-2, the mechanism of its invasion into host cells, nasal cleaning, IM vaccines and IN vaccines, and suggest increasing the development of IN vaccines, and use of IN vaccines as a supplement to IM vaccines.

SARS-CoV-2 and Influenza Co-Infection: Fair Competition or Sinister Combination?

The COVID-19 pandemic remains a serious public health problem globally. During winter influenza seasons, more aggressive SARS-CoV-2 infections and fatalities have been documented, indicating that influenza co-infections may significantly impact the disease outcome of COVID-19. Both influenza and SARS-CoV-2 viruses share many similarities in their transmission and their cellular tropism for replication in the human respiratory tract. However, the complex intricacies and multi-faceted dynamics of how the two pathogens interact to ensure their survival in the same lung microenvironment are still unclear. In addition, clinical studies on influenza co-infections in COVID-19 patients do not provide conclusive evidence of how influenza co-infection mechanistically modifies disease outcomes of COVID-19. This review discusses various viral as well as host factors that potentially influence the survival or synergism of these two respiratory pathogens in the infected lung microenvironment.

Inhibition of influenza A virus and SARS-CoV-2 infection or co-infection by griffithsin and griffithsin-based bivalent entry inhibitor

Outbreaks of acute respiratory viral diseases, such as influenza and COVID-19 caused by influenza A virus (IAV) and SARS-CoV-2, pose a serious threat to global public health, economic security, and social stability. This calls for the development of broad-spectrum antivirals to prevent or treat infection or co-infection of IAV and SARS-CoV-2. Hemagglutinin (HA) on IAV and spike (S) protein on SARS-CoV-2, which contain various types of glycans, play crucial roles in mediating viral entry into host cells. Therefore, they are key targets for the development of carbohydrate-binding protein-based antivirals. This study demonstrated that griffithsin (GRFT) and the GRFT-based bivalent entry inhibitor GL25E (GRFT-L25-EK1) showed broad-spectrum antiviral effects against IAV infection in vitro by binding to HA in a carbohydrate-dependent manner and effectively protected mice from lethal IAV infection. Although both GRFT and GL25E could inhibit infection of SARS-CoV-2 Omicron variants, GL25E proved to be significantly more effective than GRFT and EK1 alone. Furthermore, GL25E effectively inhibited in vitro co-infection of IAV and SARS-CoV-2 and demonstrated good druggability, including favorable safety and stability profiles. These findings suggest that GL25E is a promising candidate for further development as a broad-spectrum antiviral drug for the prevention and treatment of infection or co-infection from IAV and SARS-CoV-2.IMPORTANCEInfluenza and COVID-19 are highly contagious respiratory illnesses caused by the influenza A virus (IAV) and SARS-CoV-2, respectively. IAV and SARS-CoV-2 co-infection exacerbates damage to lung tissue and leads to more severe clinical symptoms, thus calling for the development of broad-spectrum antivirals for combating IAV and SARS-CoV-2 infection or co-infection. Here we found that griffithsin (GRFT), a carbohydrate-binding protein, and GL25E, a recombinant protein consisting of GRFT, a 25 amino acid linker, and EK1, a broad-spectrum coronavirus inhibitor, could effectively inhibit IAV and SARS-CoV-2 infection and co-infection by targeting glycans on HA of IAV and spike (S) protein of SARS-CoV-2. GL25E is more effective than GRFT because GL25E can also interact with the HR1 domain in SARS-CoV-2 S protein. Furthermore, GL25E possesses favorable safety and stability profiles, suggesting that it is a promising candidate for development as a drug to prevent and treat IAV and SARS-CoV-2 infection or co-infection.

SARS-CoV-2 co-detection with influenza and human respiratory syncytial virus in Ethiopia: Findings from the severe acute respiratory illness (SARI) and influenza-like illness (ILI) sentinel surveillance, January 01, 2021, to June 30, 2022

SARS-CoV-2 co-infection with the influenza virus or human respiratory syncytial virus (RSV) may complicate its progress and clinical outcomes. However, data on the co-detection of SARS-CoV-2 with other respiratory viruses are limited in Ethiopia and other parts of Africa to inform evidence-based response and decision-making. We analyzed 4,989 patients' data captured from the national severe acute respiratory illness (SARI) and influenza-like illness (ILI) sentinel surveillance sites over 18 months period from January 01, 2021, to June 30, 2022. Laboratory specimens were collected from the patients and tested for viral respiratory pathogens by real-time, reverse transcription polymerase chain reaction (RT-PCR) at the national influenza center. The median age of the patients was 14 years (IQR: 1-35 years), with a slight preponderance of them being at the age of 15 to less than 50 years. SARS-CoV-2 was detected among 459 (9.2%, 95% CI: 8.4-10.0) patients, and 64 (1.3%, 95% CI: 1.0-1.6) of SARS-CoV-2 were co-detected either with Influenza virus (54.7%) or RSV (32.8%) and 12.5% were detected with both of the viruses. A substantial proportion (54.7%) of SARS-CoV-2 co-detection with other respiratory viruses was identified among patients in the age group from 15 to less than 50 years. The multivariable analysis found that the odds of SARS-CoV-2 co-detection was higher among individuals with the age category of 20 to 39 years as compared to those less than 20 years old (AOR: 1.98, 95%CI:1.15-3.42) while the odds of SARS-CoV-2 co-detection was lower among cases from other regions of the country as compared to those from Addis Ababa (AOR:0.16 95%CI:0.07-0.34). Although the SARS-CoV-2 co-detection with other respiratory viral pathogens was minimal, the findings of this study underscore that it is critical to continuously monitor the co-infections to reduce transmission and improve patient outcomes, particularly among the youth and patients with ILI.

Multiplexed Capillary-Flow Driven Immunoassay for Respiratory Illnesses

Multiplexed analysis in medical diagnostics is widely accepted as a more thorough and complete method compared to single-analyte detection. While analytical methods like polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) exist for multiplexed detection of biomarkers, they remain time-consuming and expensive. Lateral flow assays (LFAs) are an attractive option for point-of-care testing, and examples of multiplexed LFAs exist. However, these devices are limited by spatial resolution of test lines, large sample volume requirements, cross-reactivity, and poor sensitivity. Recent work has developed capillary-flow microfluidic ELISA platforms as a more sensitive alternative to LFAs; however, multiplexed detection on these types of devices has yet to be demonstrated. In the aftermath of the initial SARS-CoV-2 pandemic, the need for rapid, sensitive point-of-care devices has become ever clearer. Moving forward, devices that can distinguish between diseases with similar presenting symptoms would be the ideal home diagnostic. Here, the first example of a multiplexed capillary-flow immunoassay device for the simultaneous detection of multiple biomarkers is reported. From a single sample addition step, the reagents and washing steps required for two simultaneous ELISAs are delivered to spatially separated test strips. Visual results can be obtained in <15 min, and images captured with a smartphone can be analyzed for quantitative data. This device was used to distinguish between and quantify H1N1 hemagglutinin (HA) and SARS-CoV-2 nucleocapsid protein (N-protein). Using this device, analytical detection limits of 840 and 133 pg/mL were obtained for hemagglutinin and nucleocapsid protein, respectively. The presence of one target in the device did not increase the signal on the other test line, indicating no cross-reactivity between the assays. Additionally, simultaneous detection of both N-protein and HA was performed as well as simultaneous detection of N-protein and human C-reactive protein (CRP). Elevated levels of CRP in a patient infected with SARS-CoV-2 have been shown to correlate with more severe outcomes and a greater risk of death as well. To further expand on the simultaneous detection of two biomarkers, CRP and N-protein were detected simultaneously, and the presence of SARS-CoV-2 N-protein did not interfere with the detection of CRP when both targets were present in the sample.

COVID-19 and flu vaccination in Romania, post pandemic lessons in healthcare workers and general population

BACKGROUND

Influenza and corona viruses generate vaccine preventable diseases and have pandemic potential, frequently dramatic. A co-infection with these viruses, may be a new worldwide threat, researchers name it flurona. The aim of our study is to assess flu and COVID-19 Romanian vaccination for 2022-2023 season and the factor associated with higher odds to receive flu and COVID-19 vaccine.

METHODS

An analytical cross-sectional observational survey was conducted in the general population; a self-administered questionnaire was used.

RESULTS

1056 responders were analyzed, mean age 32.08 ±13.36 years (limits:18-76), majority, 880 (83.33%), from urban areas, 608 (57.58%), high school graduated, 400 (37.88%) parents. More than half of the responders were healthcare workers, 582 (55.11%), also considered study population. In the study group, 796 (73.37%) responders consider flurona vaccination useful; and 872 (82.57%) responders consider that no sanctions are needed for not flurona vaccinating. In the 2022-2023 season, 162 (15.34%) responders vaccinated against the flu and 300 (28.41%) against COVID-19. The factor associated with higher odds to receive flu and COVID-19 vaccine was the habit of flu vaccination: for flu (OR = 58.43; 95% CI: (34.95-97.67)) and for COVID-19 (OR = 1.67; 95% CI: (1.21-2.31)). Other factors such as having university degree (OR = 1.46; 95% CI: (1.08-1.98)) and being a healthcare worker, (OR = 1.41; 95% CI: (1.07-1.87)) were influencing factors only for adult COVID-19 vaccination in the 2022-2023 season. In the parents' group, in 2022-2023 season, only 48 (12%) vaccinated their children against the flu and 68 (17%) against COVID-19, mostly parents that vaccinated themselves, p<0.001. In the 2022-2023 season, there were only 82 (7.65%) responders vaccinated against both diseases. Logistic regression analysis showed that no factor analyzed influenced the flurona vaccinated parent's decision to vaccinate their children for flu and for COVID-19.

CONCLUSIONS

In the season 2022-2023, in Romania, the vaccination against flu and COVOD-19 is low, in adults and children as well. More efforts must be done to increase flurona vaccination, public health educational programs are strongly needed. Children, that are at greater risk when co-infecting with these viruses, must be vaccinated, school vaccination programs should be considered.

Influenza and COVID-19 co-infection and vaccine effectiveness against severe cases: a mathematical modeling study

Background

Influenza A virus have a distinctive ability to exacerbate SARS-CoV-2 infection proven by in vitro studies. Furthermore, clinical evidence suggests that co-infection with COVID-19 and influenza not only increases mortality but also prolongs the hospitalization of patients. COVID-19 is in a small-scale recurrent epidemic, increasing the likelihood of co-epidemic with seasonal influenza. The impact of co-infection with influenza virus and SARS-CoV-2 on the population remains unstudied.

Method

Here, we developed an age-specific compartmental model to simulate the co-circulation of COVID-19 and influenza and estimate the number of co-infected patients under different scenarios of prevalent virus type and vaccine coverage. To decrease the risk of the population developing severity, we investigated the minimum coverage required for the COVID-19 vaccine in conjunction with the influenza vaccine, particularly during co-epidemic seasons.

Result

Compared to the single epidemic, the transmission of the SARS-CoV-2 exhibits a lower trend and a delayed peak when co-epidemic with influenza. Number of co-infection cases is higher when SARS-CoV-2 co-epidemic with Influenza A virus than that with Influenza B virus. The number of co-infected cases increases as SARS-CoV-2 becomes more transmissible. As the proportion of individuals vaccinated with the COVID-19 vaccine and influenza vaccines increases, the peak number of co-infected severe illnesses and the number of severe illness cases decreases and the peak time is delayed, especially for those >60 years old.

Conclusion

To minimize the number of severe illnesses arising from co-infection of influenza and COVID-19, in conjunction vaccinations in the population are important, especially priority for the elderly.

Flu-COVID combo recombinant protein vaccines elicited protective immune responses against both influenza and SARS-CoV-2 viruses infection

SARS-CoV-2 and Influenza viruses are both highly transmissible airborne viruses and causing high morbidity and mortality. Co-infection of these two viruses results in severe disease that have been observed when influenza and SARS-CoV-2 viruses cocirculated in the past three years, and vaccination is still the effective way to prevent these two diseases. However, influenza and COVID-19 vaccines are designed and manufactured in different platforms, all the individuals will need to get two shots in order to prevent those two severe respiratory diseases. Therefore, it is urgent to develop a Flu-COVID combo vaccine to provide an efficient way for receiving immunization against those two diseases. In this study, we developed a flu-COVID combo vaccine that includes both influenza virus haemagglutinin (HA) proteins and SARS-CoV-2 Spike (S) protein which formulated with AddaVax. K18-hACE-2 transgenic mice were intramuscularly vaccinated with either combo vaccine or mono Flu (HA) or COVID (S) recombinant protein vaccine in a prime-boost-boost regimen, and then were challenged with lethal doses of influenza virus or SARS-CoV-2 to evaluate vaccine efficacy. The results showed that Flu-COVID combo vaccine protected mice from both Influenza and SARS-CoV-2 challenge by preventing body weight loss and clinical signs progression. The protective immune responses elicited by Flu-COVID combo vaccine were equivalent to those elicited by mono flu or COVID recombinant protein vaccines. In conclusion, our study highlights the effectiveness of the FLU-COVID combo recombinant protein vaccine in preventing both influenza and COVID-19 infections.

Prior Influenza Infection Mitigates SARS-CoV-2 Disease in Syrian Hamsters

Seasonal infection rates of individual viruses are influenced by synergistic or inhibitory interactions between coincident viruses. Endemic patterns of SARS-CoV-2 and influenza infection overlap seasonally in the Northern hemisphere and may be similarly influenced. We explored the immunopathologic basis of SARS-CoV-2 and influenza A (H1N1pdm09) interactions in Syrian hamsters. H1N1 given 48 h prior to SARS-CoV-2 profoundly mitigated weight loss and lung pathology compared to SARS-CoV-2 infection alone. This was accompanied by the normalization of granulocyte dynamics and accelerated antigen-presenting populations in bronchoalveolar lavage and blood. Using nasal transcriptomics, we identified a rapid upregulation of innate and antiviral pathways induced by H1N1 by the time of SARS-CoV-2 inoculation in 48 h dual-infected animals. The animals that were infected with both viruses also showed a notable and temporary downregulation of mitochondrial and viral replication pathways. Quantitative RT-PCR confirmed a decrease in the SARS-CoV-2 viral load and lower cytokine levels in the lungs of animals infected with both viruses throughout the course of the disease. Our data confirm that H1N1 infection induces rapid and transient gene expression that is associated with the mitigation of SARS-CoV-2 pulmonary disease. These protective responses are likely to begin in the upper respiratory tract shortly after infection. On a population level, interaction between these two viruses may influence their relative seasonal infection rates.

Influence of COVID-19 over seasonal influenza activity in southern India

Basic epidemiological data is urgently needed in order to ascertain the changes brought about by COVID-19 pandemic, and help researchers, clinicians, and policy makers in addressing these issues. Data on influenza positivity from 2009 to 2019 was collected from Regional Influenza laboratory, JIPMER. Being COVID testing centre we tested samples (2020-2023) from Tamilnadu and Pondicherry. All SARI samples which were negative for COVID-19 were subjected to Influenza testing as regular surveillance activity was suspended. On comparison we found significant reduction in detection rates of influenza A H1N1, H3N2 and influenza B (p value = <0.01).

Adult risk groups for vaccine preventable respiratory infections: an overview of the UK environment

INTRODUCTION

Vaccine-preventable respiratory infections (VPRI) including those caused by Streptococcus pneumoniae, influenza, respiratory syncytial virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pose substantial challenges to health and social care systems. In the UK, routine adult respiratory vaccination programs are in place. The objective of this article is to review the current evidence on the impact of four seasonal VPRIs in adults risk group definitions and to explore the strengths and limitations of current recommendations, and to identify evidence gaps for further research.

AREAS COVERED

Relevant evidence on UK data from surveillance systems, observational studies and publicly available government documents is collated and reviewed, as well as selected global data.

EXPERT OPINION

Disparities exist between adult risk group categories for different respiratory vaccination programs as defined in the current vaccination guidance. The burden of multiple respiratory pathogens signifies importance of routine multi-pathogen testing with the need for a resilient and large-scale national surveillance system. Further understanding of epidemiological trends and disease burden will help guide decision-making and planning of targeted strategies for disease prevention and control. Addressing inequalities in disease burden and vaccine coverage particularly in clinical risk groups, and promoting equitable vaccine access remain a priority.

Influenza-A mediated pre-existing immunity levels to SARS-CoV-2 could predict early COVID-19 outbreak dynamics

Susceptibility to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections is highly variable and could be mediated by a cross-protective pre-immunity. We identified 14 cross-reactive peptides between SARS-CoV-2 and influenza A H1N1, H3N2, and human herpesvirus (HHV)-6A/B with potential relevance. The H1N1 peptide NGVEGF was identical to a peptide in the most critical receptor binding motif in SARS-CoV-2 spike protein that interacts with the angiotensin converting enzyme 2 receptor. About 62%-73% of COVID-19-negative blood donors in Stockholm had antibodies to this peptide in the early pre-vaccination phase of the pandemic. Seasonal flu vaccination enhanced neutralizing capacity to SARS-CoV-2 and T cell immunity to this peptide. Mathematical modeling taking the estimated pre-immunity levels to flu into account could fully predict pre-Omicron SARS-CoV-2 outbreaks in Stockholm and India. This cross-immunity provides mechanistic explanations to the epidemiological observation that influenza vaccination protected people against early SARS-CoV-2 infections and implies that flu-mediated cross-protective immunity significantly dampened the first SARS-CoV-2 outbreaks.

Monoglycosylated SARS-CoV-2 receptor binding domain fused with HAstem-scaffolded protein vaccine confers broad protective immunity against SARS-CoV-2 and influenza viruses

The SARS-CoV-2 and influenza pandemics have posed a devastating threat to global public health. The best strategy for preventing the further spread of these respiratory viruses worldwide is to administer a vaccine capable of targeting both viruses. Here, we show that a novel monoglycosylated vaccine designed based on the influenza virus HAstem conserved domain fused with the SARS-CoV-2 spike-RBD domain (HSSRmg) can present proper antigenicity that elicits sufficient neutralization efficacy against various SARS-CoV-2 variants while simultaneously providing broad protection against H1N1 viruses in mice. Compared with the fully glycosylated HSSR (HSSRfg), HSSRmg induced higher ELISA titers targeting HAstem and spike-RBD and exhibited significantly enhanced neutralization activity against the Wuhan pseudovirus. The enhanced immune responses raised by JR300-adjuvanted HSSRmg compared to HSSRmg alone include more anti-HAstem and anti-spike-RBD antibodies that provide cross-protection against H1N1 challenges and cross-neutralization of SARS-CoV-2 pseudoviruses. Furthermore, the enhanced immune response raised by JR300-adjuvanted-HSSRmg skews toward a more balanced Th1/Th2 response than that raised by HSSRmg alone. Notably, HSSRmg elicited more plasma B cells and memory B cells, and higher IL-4 and IFN-γ cytokine immune responses than spike (S-2P) in mice with preexisting influenza-specific immunity, suggesting that B-cell activation most likely occurs through CD4+ T-cell stimulation. This study demonstrated that HSSRmg produced using a monoglycosylation process and combined with the JR300 adjuvant elicits superior cross-strain immune responses against SARS-CoV-2 and influenza viruses in mice compared with S-2P. JR300-adjuvanted HSSRmg has great potential as a coronavirus-influenza vaccine that provides dual protection against SARS-CoV-2 and influenza infections.

Assessing the influence of COVID-19 on influenza prevalence: A multicenter time series study

BACKGROUND

During the COVID-19 pandemic, countries around the world implemented various interventions to manage the spread of respiratory illnesses, including influenza. However, there is a lack of studies that have assessed the influence of COVID-19 on influenza prevalence in Saudi Arabia. In this study, we aimed to evaluate the prevalence of positive influenza cases before and during the COVID-19 pandemic in relation to the mitigation measures and policy initiatives in Saudi Arabia.

METHODS

A multicenter, time-series cross-sectional study was conducted to evaluate influenza prevalence before and during the COVID-19 pandemic between 01/01/2017 and 31/12/2021. This study included all patients who were screened for influenza infection at healthcare facilities across Saudi Arabia using polymerase chain reaction (PCR). The primary outcome was to determine the prevalence of influenza infections before and during the COVID-19 pandemic, while the secondary outcome was to describe the demographic data and comorbidities of the included patients in both periods.

RESULTS

During the study period, 5238 cases were identified based on a positive PCR result for influenza virus. The yearly number of influenza cases in the pre-COVID-19 period was 1123 (2.03 %), 1075 (1.63 %), and 1883 (2.20 %) cases in 2017, 2018, and 2019, respectively. On the other hand, the number of cases during the COVID-19 pandemic was 417 (0.63 %) and 740 (1.27 %) in 2020 and 2021, respectively, with a comparable number of performed tests. Patients infected with the influenza virus between 2020 and 2021 were older than patients who were infected before the COVID-19 pandemic.

CONCLUSION

The study found a lower number of influenza cases during the COVID-19 pandemic, with no clear peak during November and December 2020 and 2021.

A systematic review of the clinical characteristics of influenza-COVID-19 co-infection

COVID-19 has impacted populations across the globe and has been a major cause of morbidity and mortality. Influenza is another potentially deadly respiratory infection that affects people worldwide. While both of these infections pose major health threats, little is currently understood regarding the clinical aspects of influenza and COVID-19 co-infection. Our objective was to therefore provide a systematic review of the clinical characteristics, treatments, and outcomes for patients who are co-infected with influenza and COVID-19. Our review, which was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, involved searching for literature in seven different databases. Studies were eligible for inclusion if they included at least one co-infected patient, were available in English, and described clinical characteristics for the patients. Data were pooled after extraction. Study quality was assessed using the Joanna Brigg's Institute Checklists. Searches produced a total of 5096 studies, and of those, 64 were eligible for inclusion. A total of 6086 co-infected patients were included, 54.1% of whom were male; the mean age of patients was 55.9 years (SD = 12.3). 73.6% of cases were of influenza A and 25.1% were influenza B. 15.7% of co-infected patients had a poor outcome (death/deterioration). The most common symptoms were fever, cough, and dyspnea, with the most frequent complications being pneumonia, linear atelectasis, and acute respiratory distress syndrome. Oseltamivir, supplemental oxygen, arbidol, and vasopressors were the most common treatments provided to patients. Having comorbidities, and being unvaccinated for influenza, were shown to be important risk factors. Co-infected patients show symptoms that are similar to those who are infected with COVID-19 or influenza only. However, co-infected patients have been shown to be at an elevated risk for poor outcomes compared to mono-infected COVID-19 patients. Screening for influenza in high-risk COVID-19 patients is recommended. There is also a clear need to improve patient outcomes with more effective treatment regimens, better testing, and higher rates of vaccination.

The Impact of the COVID-19 Pandemic on Influenza Vaccination Attitudes and Actions in Spain's Adult Population

Seasonal influenza is an acute respiratory infection caused by the influenza virus which constitutes a significant public health issue associated with high morbidity and mortality. The aim of this study was to investigate changes in attitudes, perceptions, and practices regarding influenza vaccination in the Spanish adult population during the COVID-19 pandemic, as well as their vaccination intentions, with special attention paid to those over 65 years old and in high-risk groups. To this end, a cross-sectional study was conducted through 2219 telephone interviews, and the results were compared with results obtained a year earlier. Regarding the reasons for deciding to get vaccinated in the 2022/23 season, a significant increase was observed in vaccine confidence (36.7% vs. 42.8%), social responsibility (32.5% vs. 43.8%), and in awareness of the importance of vaccination due to COVID-19 (21.7% vs. 25.4%). Advanced age (OR 2.8, 95% CI 2.0-3.9), belonging to high-risk groups (OR 2.7, 95% CI 2.0-3.7), and prior vaccination (OR 25.3, 95% CI 19.5-32.7) emerged as significant predictors for the intent to receive the influenza vaccine in the 2022/23 season. Continuously observing shifts in perceptions and behaviors related to influenza immunization is crucial to pinpoint factors that may influence the willingness to receive the vaccine and, in this way, design public health strategies that achieve a greater acceptance of it.

Flurona: The First Autopsied Case

COVID-19-associated coinfections increase the patient's risk of developing a severe form of the disease and, consequently, the risk of death. The term "flurona" was proposed to describe the coinfection of the influenza virus and SARS-CoV-2. This report is about a case of a 7-month-old female infant who died due to flurona coinfection. A histopathological exam showed activation of microglia (becoming CD45 positive), bronchial inflammation, diffuse alveolar damage in proliferative phase with vasculitis, a peribronchial infiltrate that was predominantly CD20-positive, and a vascular wall infiltrate that was predominantly CD3-positive. The aggressiveness of the two respiratory viruses added up and they caused extensive lung inflammation, which led to respiratory failure, multiple organ failure, and death. Tissues injuries caused by both the influenza virus and SARS-CoV-2 could be observed, without the ability to certify the dominance of the aggression of one of the two viruses.

Shifting Patterns of Influenza Circulation during the COVID-19 Pandemic, Senegal

Historically low levels of seasonal influenza circulation were reported during the first years of the COVID-19 pandemic and were mainly attributed to implementation of nonpharmaceutical interventions. In tropical regions, influenza's seasonality differs largely, and data on this topic are scarce. We analyzed data from Senegal's sentinel syndromic surveillance network before and after the start of the COVID-19 pandemic to assess changes in influenza circulation. We found that influenza shows year-round circulation in Senegal and has 2 distinct epidemic peaks: during January-March and during the rainy season in August-October. During 2021-2022, the expected January-March influenza peak completely disappeared, corresponding to periods of active SARS-CoV-2 circulation. We noted an unexpected influenza epidemic peak during May-July 2022. The observed reciprocal circulation of SARS-CoV-2 and influenza suggests that factors such as viral interference might be at play and should be further investigated in tropical settings.

Co-infection of SARS-CoV-2 with human coronavirus OC43 in a patient with underlying lung disease: A case report

Co-infections with SARS-CoV-2 remain relatively rare and there is limited published data on the consequences of these events. We present the case of a 26-year-old man with SARS-CoV-2 and human coronavirus OC43 who had a severe infection resulting in prolonged hospitalization. Consideration of co-infections should be considered in high-risk patients.

Evaluating socioeconomic inequalities in influenza vaccine uptake during the COVID-19 pandemic: A cohort study in Greater Manchester, England

BACKGROUND

There are known socioeconomic inequalities in annual seasonal influenza (flu) vaccine uptake. The Coronavirus Disease 2019 (COVID-19) pandemic was associated with multiple factors that may have affected flu vaccine uptake, including widespread disruption to healthcare services, changes to flu vaccination eligibility and delivery, and increased public awareness and debate about vaccination due to high-profile COVID-19 vaccination campaigns. However, to the best of our knowledge, no existing studies have investigated the consequences for inequalities in flu vaccine uptake, so we aimed to investigate whether socioeconomic inequalities in flu vaccine uptake have widened since the onset of the COVID-19 pandemic.

METHODS AND FINDINGS

We used deidentified data from electronic health records for a large city region (Greater Manchester, population 2.8 million), focusing on 3 age groups eligible for National Health Service (NHS) flu vaccination: preschool children (age 2 to 3 years), primary school children (age 4 to 9 years), and older adults (age 65 years plus). The sample population varied between 418,790 (2015/16) and 758,483 (2021/22) across each vaccination season. We estimated age-adjusted neighbourhood-level income deprivation-related inequalities in flu vaccine uptake using Cox proportional hazards models and the slope index of inequality (SII), comparing 7 flu vaccination seasons (2015/16 to 2021/22). Among older adults, the SII (i.e., the gap in uptake between the least and most income-deprived areas) doubled over the 7 seasons from 8.48 (95% CI [7.91,9.04]) percentage points to 16.91 (95% CI [16.46,17.36]) percentage points, with approximately 80% of this increase occurring during the pandemic. Before the pandemic, income-related uptake gaps were wider among children, ranging from 15.59 (95% CI [14.52,16.67]) percentage points to 20.07 (95% CI [18.94,21.20]) percentage points across age groups and vaccination seasons. Among preschool children, the uptake gap increased in 2020/21 to 25.25 (95% CI [24.04,26.45]) percentage points, before decreasing to 20.86 (95% CI [19.65,22.05]) percentage points in 2021/22. Among primary school children, inequalities increased in both pandemic years to reach 30.27 (95% CI [29.58,30.95]) percentage points in 2021/22. Although vaccine uptake increased during the pandemic, disproportionately larger increases in uptake in less deprived areas created wider inequalities in all age groups. The main limitation of our approach is the use of a local dataset, which may limit generalisability to other geographical settings.

CONCLUSIONS

The COVID-19 pandemic led to increased inequalities in flu vaccine uptake, likely due to changes in demand for vaccination, new delivery models, and disruptions to healthcare and schooling. It will be important to investigate the causes of these increased inequalities and to examine whether these increased inequalities also occurred in the uptake of other routine vaccinations. These new wider inequalities in flu vaccine uptake may exacerbate inequalities in flu-related morbidity and mortality.

Associations between COVID-19 Vaccination and Behavioural Intention to Receive Seasonal Influenza Vaccination among Chinese Older Adults: A Population-Based Random Telephone Survey

During the Coronavirus Disease 2019 (COVID-19) pandemic, seasonal influenza remained a significant health threat for older adults. Seasonal influenza vaccination (SIV) is highly effective and safe for older adults. This study investigated the associations of COVID-19 vaccination, perceptions related to COVID-19 and SIV, with the behavioural intention to receive SIV among older adults in Hong Kong, China. A random telephone survey was conducted among 440 community-dwelling Hong Kong residents aged 65 years or above, between November 2021 and January 2022. Among the participants, 55.7% intended to receive SIV in the next year. After adjustment for significant background characteristics, concern about whether SIV and COVID-19 vaccination would negatively affect each other was associated with a lower intention to receive SIV, while a perceived higher risk of co-infection with COVID-19 and seasonal influenza was positively associated with the dependent variable. In addition, the perceived severe consequences of seasonal influenza, perceived benefits of SIV, received cues to action from doctors and participants' family members or friends, and the perception that more older people would receive SIV was associated with a higher behavioural intention. Future programmes promoting SIV among older adults should modify perceptions related to COVID-19 vaccination and SIV at the same time.