Prediction of hospital-acquired influenza using machine learning algorithms: a comparative study

BACKGROUND

Hospital-acquired influenza (HAI) is under-recognized despite its high morbidity and poor health outcomes. The early detection of HAI is crucial for curbing its transmission in hospital settings.

AIM

This study aimed to investigate factors related to HAI, develop predictive models, and subsequently compare them to identify the best performing machine learning algorithm for predicting the occurrence of HAI.

METHODS

This retrospective observational study was conducted in 2022 and included 111 HAI and 73,748 non-HAI patients from the 2011-2012 and 2019-2020 influenza seasons. General characteristics, comorbidities, vital signs, laboratory and chest X-ray results, and room information within the electronic medical record were analysed. Logistic Regression (LR), Random Forest (RF), Extreme Gradient Boosting (XGB), and Artificial Neural Network (ANN) techniques were used to construct the predictive models. Employing randomized allocation, 80% of the dataset constituted the training set, and the remaining 20% comprised the test set. The performance of the developed models was assessed using metrics such as the area under the receiver operating characteristic curve (AUC), the count of false negatives (FN), and the determination of feature importance.

RESULTS

Patients with HAI demonstrated notable differences in general characteristics, comorbidities, vital signs, laboratory findings, chest X-ray result, and room status compared to non-HAI patients. Among the developed models, the RF model demonstrated the best performance taking into account both the AUC (83.3%) and the occurrence of FN (four). The most influential factors for prediction were staying in double rooms, followed by vital signs and laboratory results.

CONCLUSION

This study revealed the characteristics of patients with HAI and emphasized the role of ventilation in reducing influenza incidence. These findings can aid hospitals in devising infection prevention strategies, and the application of machine learning-based predictive models especially RF can enable early intervention to mitigate the spread of influenza in healthcare settings.

Covid-19 and influenza vaccine effectiveness against associated hospital admission and death among individuals over 65 years in Norway: A population-based cohort study, 3 October 2022 to 20 June 2023

BACKGROUND

Co-circulation of SARS-CoV-2 and influenza virus can lead to double epidemics and increased pressure on health systems. To evaluate the effect of both vaccines, we estimated the adjusted vaccine effectiveness (aVE) of influenza and Covid-19 vaccines against related severe disease in the elderly population in Norway during the 2022/2023 season.

METHODS

In this population-based cohort study, we included data from the Emergency preparedness register for Covid-19 (Beredt C19) on all individuals ≥ 65 years living in Norway between 3 October 2022 and 20 June 2023. Using Cox-proportional hazard models, we estimated aVE of both influenza and Covid-19 vaccines (bivalent BA.1 and BA.4-5) against associated hospitalisation and death. Vaccine status was included as a time-varying covariate and all models were adjusted for potential confounders, including the other vaccine.

RESULTS

We identified 2,437 influenza-associated hospitalisations and 178 deaths, alongside 5,824 Covid-19-associated hospitalisations and 621 deaths. The aVE was highest in the first three months after receiving either vaccine. Against influenza-associated hospitalisation the aVE was 34 % (26 %-42 %) among 65-79-year-olds and 40 % (30 %-48 %) among ≥ 80-year-olds, and 6.6 % (-64 %-47 %) and 37 % (0.5 %-61 %) against influenza-associated death, respectively. The aVE against Covid-19-associated hospitalisation was 65 % (61 %-69 %) among 65-79-year-olds and 55 % (49 %-60 %) among ≥ 80-year-olds (compared to having received the vaccine ≥ 180 days ago). Similarly, the aVE against Covid-19-associated death was 68 % (48 %-80 %) and 78 % (65 %-86 %), respectively. For Covid-19 we show a reduction in aVE with time since dose.

CONCLUSION

Covid-19 and influenza vaccines reduced the risk of severe disease in the same high-risk population. Ensuring high uptake of both vaccines could thus limit the overall health care burden.

Evaluating the performance of WHO and CDC case definitions for influenza-like illness in diagnosing influenza during the 2022-2023 flu season in Mexico

OBJECTIVE

This study aimed to evaluate the performance of the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) case definitions for influenza-like illness (ILI) in diagnosing influenza during the 2022-2023 flu season in Mexico.

STUDY DESIGN

We conducted a cross-sectional analysis of national epidemiological surveillance data in Mexico, focusing on respiratory viral pathogens.

METHODS

We analyzed data from 6027 non-hospitalized patients between 5 and 65 years old who underwent molecular testing for respiratory viral pathogens. The performance of both case definitions was evaluated in terms of sensitivity, specificity, and the area under the receiver operating characteristic (AUROC) curve.

RESULTS

Overall, the diagnostic accuracy of the evaluated ILI definitions in identifying influenza patients was low, particularly among older patients. When compared to the CDC, the WHO definition had a lower sensitivity but a higher specificity, resulting in a higher AUROC (P = 0.031) for the WHO criteria.

CONCLUSIONS

Our findings suggest that the WHO and CDC ILI case definitions have limited accuracy for diagnosing influenza in non-hospitalized patients and highlight the need for more specific diagnostic tools to improve the detection of influenza cases during the flu season.

Survival in influenza virus-related pneumonia by viral subtype: 2016-2020

BACKGROUND

Influenza remains a common cause of morbidity and mortality worldwide, and viral subtype-related differences in disease outcomes have been documented.

OBJECTIVE

To characterize the survival experience of adult inpatients with influenza virus-associated pneumonia by viral subtype during five consecutive flu seasons.

METHOD

We performed a retrospective cohort study; data from 4,678 adults were analyzed using the Kaplan-Meier method. A multivariate Cox proportional hazard regression model was fitted.

RESULTS

The overall in-hospital mortality rate was 25.0 per 1,000 hospital days. The survival probabilities from pneumonia patients went from 93.4% (95% CI 92.6-94.1%) by day three to 43.3% (95% CI 39.2-47.4%) by day 30 from hospital admission. In general, the lowest survival rates were observed in patients with AH1N1 infection. In multiple models, after adjusting for comorbidities and when compared with A non-subtyped virus, pneumonia patients with AH3N2 or B strains had a significantly decreased risk of a non-favorable disease outcome. The association of other strains was not significant.

CONCLUSIONS

Our findings suggest that the survival of inpatients with influenza virus-associated pneumonia varies according to the pathogenic viral subtype; the lowest survival rates were observed in patients with AH1N1 infection. This effect was independent of the patients' gender, age, and the analyzed underlying health conditions.

Diagnostic Accuracy of the Quidel Sofia Rapid Influenza Fluorescent Immunoassay in Patients with Influenza-like Illness: A Systematic Review and Meta-analysis

Background

Although the Quidel Sofia rapid influenza fluorescent immunoassay (FIA) is widely used to identify influenza A and B, the diagnostic accuracy of this test remains unclear. Thus, the objective of this study was to determine the diagnostic performance of this test compared to reverse transcriptase-polymerase chain reaction.

Methods

A systematic literature search was performed using MEDLINE, EMBASE, and the Cochrane Central Register. Pooled sensitivity, specificity, diagnostic odds ratio (DOR), and a hierarchical summary receiver-operating characteristic curve (HSROC) of this test for identifying influenza A and B were determined using meta-analysis. A sensitivity subgroup analysis was performed to identify potential sources of heterogeneity within selected studies.

Results

We identified 17 studies involving 8,334 patients. Pooled sensitivity, specificity, and DOR of the Quidel Sofia rapid influenza FIA for identifying influenza A were 0.78 (95% confidence interval [CI], 0.71–0.83), 0.99 (95% CI, 0.98–0.99), and 251.26 (95% CI, 139.39–452.89), respectively. Pooled sensitivity, specificity, and DOR of this test for identifying influenza B were 0.72 (95% CI, 0.60–0.82), 0.98 (95% CI, 0.96–0.99), and 140.20 (95% CI, 55.92–351.54), respectively. The area under the HSROC for this test for identifying influenza A was similar to that for identifying influenza B. Age was considered a probable source of heterogeneity.

Conclusion

Pooled sensitivities of the Quidel Sofia rapid influenza FIA for identifying influenza A and B did not quite meet the target level (≥80%). Thus, caution is needed when interpreting data of this study due to substantial between-study heterogeneity.

[Influenza Vaccination in Patients with Cardiovascular Disease Under 65 in the COVID-19 Era]

N/a.

Implementing an Influenza Vaccine Effectiveness Study in a Hospital Context in Portugal: The EVA Hospital Project

INTRODUCTION

The project 'Integrated Monitoring of Vaccines in Europe' aimed to measure seasonal influenza vaccine effectiveness against hospitalised adults, aged 65 years and over, with influenza. We describe the protocol implementation in Portugal.

MATERIAL AND METHODS

We implemented a test-negative design, targeting community-dwelling patients aged 65 years old and over hospitalised with severe acute respiratory illness. Patients were reverse transverse-polymerase chain reaction tested for influenza. Cases were those positive for influenza while others were controls. Most variables were collected using hospital medical records. Selection bias was evaluated by comparison with the laboratory influenza test requests database according to demographic characteristics. Crude, season-adjusted influenza vaccine effectiveness was estimated as = 1 - odds ratio, and 95% confidence intervals were obtained by conditional logistical regression, matched with the disease onset month.

RESULTS

The recruitment rate was 37.8%. Most participants (n = 368) were female (55.8%) and aged 80 years old and over (55.8%). This was similar to values for potentially eligible severe acute respiratory illness patients (80 years old and over: 56.8%, female: 56.2%). The proportion of missing values was below 2.5% for 20 variables and above 5% (maximum 11.6%) for six variables. Influenza vaccine effectiveness estimates were 62.1% against AH1pdm09 (95% confidence intervals: -28.1 to 88.8), 14.9% against A(H3N2) (95% confidence intervals: -69.6 to 57.3), 43.6% against B/Yam (95% confidence intervals: -66.2 to 80.8).

DISCUSSION

Given the non-existence of a coded admission database in either participating hospital the selection of severe acute respiratory illness due to clinical features was the feasible one. These results are only valid for the older adult population residing in the catchment area of the two participating hospitals who were admitted to a public hospital with severe influenza or SARI symptoms.

CONCLUSION

Despite the low participation rate, we observed comparable characteristics of participants and eligible severe acute respiratory illness patients. Data quality was high, and influenza vaccine effectiveness results were in accordance with the results of meta-analyses and European season-specific estimates. The final sample size was low, which inhibited obtaining estimates with good precision.

Reminder: Cardiovascular Patients Also Benefit from Influenza Vaccine

N/a.

[COVID-19 and Seasonal Flu During the Autumn-Winter of 2020/2021 and the Challenges Lying Ahead for Hospitals]

The possibility of a second wave of the COVID-19 pandemic coexisting with a simultaneous epidemic of influenza and the co-circulation of other seasonal respiratory viruses sets the stage for a perfect storm. Preparing for the Autumn-Winter of 2020/2021 is complex, requiring centralized guidance but local and regional solutions, with strong leadership and a high level of coordination. It is essential to act upstream of hospitals in order to reduce demand on emergency departments, minimizing the risk of transmission that occurs there and the team overload, as well as downstream to ensure capacity for hospitalization and in the hospital itself to optimize resources and organization. The failure of this plan will create unbearable pressure on hospital care. The authors describe the challenges lying ahead for hospitals and the most important measures that should be included in this plan to prepare the Autumn-Winter of 2020/2021 in Portugal.

Pre-exposure prophylaxis during the SARS-CoV-2 pandemic: can PrEP prevent COVID-19-related symptoms?

It has been speculated that some drugs can be used against SARS-CoV-2. As for antiretrovirals, the follow-up of pre-exposure prophylaxis (PrEP) users during the coronavirus disease 2019 (COVID-19) outbreak may help to understand the potential protective effect of PrEP against SARS-CoV-2. We aimed to identify associations between oral PrEP use and COVID-19-related symptoms self-reporting. Phone call interviews or digital investigation (through WhatsApp^® or e-mail) about oral PrEP regular use, social distancing, exposure to suspected or confirmed cases of SARS-CoV-2 infection and COVID-19-related symptoms. Among 108 individuals, the majority were cisgender, white and gay men. Although most of the individuals engaged in social distancing (68.52%), they kept on taking PrEP (75.93%). Few people have had contact with suspected or confirmed cases of COVID-19 (12.04%), but some had COVID-19-related symptoms the month before the interview (27.78%) including rhinorrheoa (56.67%), cough (53.33%), asthaenia (50.00%) and headache (43.33%). Also, oral PrEP was associated with lower self-reporting COVID-19-symptoms (OR 0.26, 95% CI 0.07–0.96, P = 0.04; h = 0.92) even after controlling confounders as social distancing, age, body-mass index and morbidities . In our sample, the regular use of oral PrEP was associated with lower self-reporting of COVID-19-related symptoms during the outbreak in São Paulo, Brazil.

High-Dose Seasonal Influenza Vaccine in Patients Undergoing Dialysis

BACKGROUND AND OBJECTIVES

High-dose influenza vaccine, which contains fourfold more antigen than standard dose, is associated with fewer cases of influenza and less influenza-related morbidity in the elderly general population. Whether the high-dose influenza vaccine benefits patients on dialysis, whose immune response to vaccination is less robust than that of healthy patients, is uncertain.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We compared hospitalizations and deaths during the 2015-2016 and 2016-2017 influenza seasons by vaccine type (standard trivalent, standard quadrivalent, and high-dose trivalent influenza vaccine) administered within a national dialysis organization. The association of vaccine type with outcomes was estimated using Cox proportional hazards regression with adjustment for patient factors and "center effect." Analyses were stratified by age and dialysis modality.

RESULTS

Between September 1 and December 31, 2015, standard dose trivalent, standard dose quadrivalent, and high-dose trivalent influenza vaccines were administered to 3057 (31%), 5981 (61%), and 805 (8%) patients, respectively. The adjusted rates of first hospitalizations by vaccine type during the influenza season were 8.43, 7.88, and 7.99 per 100 patient-months, respectively, and the adjusted rates of death were 1.00, 0.97, and 1.04, respectively. These differences were not significant. In 2016, 3614 (39%) received quadrivalent vaccine, and 5700 (61%) received high-dose trivalent vaccine. The adjusted rates of first hospitalization by vaccine type were 8.71 and 8.04 per 100 patient-months, respectively, and the adjusted rates of death were 0.98 and 1.02, respectively. Receipt of high dose was associated with a significant reduction in hospitalization (hazard ratio, 0.93; 95% confidence interval, 0.86 to 1.00; P=0.04); there was no significant association with death. There was no significant heterogeneity of either association by age group or dialysis modality.

CONCLUSIONS

Receipt of high-dose compared with standard dose influenza vaccine in 2016-2017 was associated with lower rates of hospitalization in patients on dialysis, although that was not seen in 2015-2016.

Strategies to maximize influenza vaccine impact in older adults

Older adults are disproportionately affected by influenza morbidity and mortality. In most high income countries, influenza vaccine policies target persons age ≥65 years for influenza vaccination. Many low-resource settings do not utilize seasonal influenza vaccination. Barriers to influenza prevention among older adults around the globe are multiple and some vary between high- and low-resource settings. To maximize influenza prevention in the older adult population, gaps in influenza vaccination coverage and improvements in vaccine efficacy are needed. The focus of this article is on the data for currently available vaccine strategies to maximize influenza vaccine impact, with a focus on high-resource settings. We also discuss novel influenza vaccine strategies needed for older adults worldwide.

A Snapshot of Influenza Surveillance, Vaccine Recommendations, and Vaccine Access, Drivers, and Barriers in Selected Middle Eastern and North African Countries

Objectives

Influenza is a vaccine-preventable acute respiratory viral infection that causes epidemics annually around the globe. A regional influenza stakeholder network (MENA-ISN) comprised of experts assessed the status of influenza prevention and control using a structured survey.

Methods

A survey questionnaire was used to obtain information from each participating country on surveillance system, the burden of disease, influenza vaccination programs, recommendations, funding and access for vaccine and vaccination, target rate, coverage rate monitoring, and drivers and barriers to influenza vaccination.

Results

Out of the 10 countries that participated, nine had an influenza surveillance system and vaccination policy, and seven had World Health Organization (WHO) accredited reference laboratory. Three countries had burden of disease data available and eight had a reimbursement vaccine policy. Influenza vaccine was available in five countries through the Ministry of Health whereas in others, pharmacies also dispensed for the private sector. In all countries, prescribers were physicians, and vaccinators, which could be physicians, nurses, and pharmacists. Eight countries had a set vaccination target rate and only three monitored the influenza coverage rates. Drivers and barriers of vaccination were similar in all countries.

Conclusions

Despite existing policies, influenza vaccination coverage remains far below the WHO recommendations. Increased awareness and effective implementation of policies with collaboration of stakeholders can help increase the rates to reach WHO targets.

The Diagnosis-Wide Landscape of Hospital-Acquired AKI

BACKGROUND AND OBJECTIVES

The exploration of electronic hospital records offers a unique opportunity to describe in-depth the prevalence of conditions associated with diagnoses at an unprecedented level of comprehensiveness. We used a diagnosis-wide approach, adapted from phenome-wide association studies (PheWAS), to perform an exhaustive analysis of all diagnoses associated with hospital-acquired AKI (HA-AKI) in a French urban tertiary academic hospital over a period of 10 years.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We retrospectively extracted all diagnoses from an i2b2 (Informatics for Integrating Biology and the Bedside) clinical data warehouse for patients who stayed in this hospital between 2006 and 2015 and had at least two plasma creatinine measurements performed during the first week of their stay. We then analyzed the association between HA-AKI and each International Classification of Diseases (ICD)-10 diagnostic category to draw a comprehensive picture of diagnoses associated with AKI. Hospital stays for 126,736 unique individuals were extracted.

RESULTS

Hemodynamic impairment and surgical procedures are the main factors associated with HA-AKI and five clusters of diagnoses were identified: sepsis, heart diseases, polytrauma, liver disease, and cardiovascular surgery. The ICD-10 code corresponding to AKI (N17) was recorded in 30% of the cases with HA-AKI identified, and in this situation, 20% of the diagnoses associated with HA-AKI corresponded to kidney diseases such as tubulointerstitial nephritis, necrotizing vasculitis, or myeloma cast nephropathy. Codes associated with HA-AKI that demonstrated the greatest increase in prevalence with time were related to influenza, polytrauma, and surgery of neoplasms of the genitourinary system.

CONCLUSIONS

Our approach, derived from PheWAS, is a valuable way to comprehensively identify and classify all of the diagnoses and clusters of diagnoses associated with HA-AKI. Our analysis delivers insights into how diagnoses associated with HA-AKI evolved over time. On the basis of ICD-10 codes, HA-AKI appears largely underestimated in this academic hospital.

Bias in the measure of the effectiveness of seasonal influenza vaccination among diabetics

BACKGROUND

The influenza virus is an important cause of morbidity and mortality for diabetics. The seasonal influenza vaccine's immunologic effectiveness is proven within the type 1 and type 2 diabetic populations, but the level of evidence is low. This article presents a systematic review for the bias in the measure of the effectiveness of seasonal influenza vaccination among diabetics.

METHODS

Using systematic review methods, we searched three electronic databases for published literature (MEDLINE, EMBASE and the Cochrane Library) and two grey literature (SIGLE and NHS EED) databases, to identify studies published between 1997 and 2013, examining the effect of seasonal influenza vaccination, among diabetics, on any measure for influenza morbidity or mortality.

RESULTS

725 records were identified from the three databases and screening, short-listing was undertaken independently by two reviewers. After de-duplication, all records were screened by title and then abstract, and 34 short-listed records were reviewed in full, with 7 studies included: 4 cohort studies and 3 case-control studies, conducted in 7 countries. The most common outcome of interest in studies (n=4) was all-cause mortality among elderly diabetics (>65 years), with individual studies reporting reductions in risk of between 33% [95%CI: 4%-54%] and 68% [95%CI: 58%-75%]. We found only two studies for working-age adult diabetics: one reporting that vaccination prevented hospitalizations due to pneumonia or influenza (vaccine effectiveness [VE] 43%, [95%CI: 28%-54%]) and all-cause hospitalizations (VE: 28% [95%CI: 24%-32%]); and, another reporting no significant decrease in all-cause mortality for working-age adult diabetics. We have identified three major biases: the use of indirect health outcomes, a risk of selection bias (health-seeking bias), and no adjustment for participant pneumococcal vaccination status. The most recent included article finds that morbimortality is still lower during off-season influenza in both vaccinated and non-vaccinated diabetics, indicating important residual confounding.

CONCLUSION

To date, the strength of evidence supporting the routine use of seasonal influenza vaccination is low for diabetics older than 65, and very low for working-age diabetics.

Pandemic Influenza A H1N1 in Oman: Epidemiology, Clinical Features, and Outcome of Patients Admitted to Sultan Qaboos University Hospital in 2009

OBJECTIVES

Oman experienced the H1N1 pandemic in 2009 that initially started in Mexico and the United States. We present the epidemiology, clinical features, and outcome of cases admitted to Sultan Qaboos University Hospital.

METHODS

We retrospectively reviewed all patients admitted with confirmed influenza A H1N1 infection from August to December 2009. The study included adults and pediatric patients. We looked at the clinical and laboratory factors associated with increased length of hospital stay.

RESULTS

There were 68 patients admitted with influenza A H1N1 infection, and their median age was 23 years. The most common symptoms were fever (100%) and cough (79.4%). The most common reason for admission was the severity of illness (69.1%). Lymphopenia was the most common hematological abnormality (41.8%). All patients received treatment with oseltamivir. One patient died secondary to multi-organ failure. On multivariate analysis, severity of illness, use of steroids, anemia, lymphopenia, and abnormal alanine amino transferase levels were associated with increased length of stay.

CONCLUSIONS

The H1N1 pandemic in Oman followed the international trends in terms of clinical presentation and laboratory values for patients admitted to the hospital.

Transcriptional signatures of influenza A/H1N1-specific IgG memory-like B cell response in older individuals

BACKGROUND

Studies suggest that the recall-based humoral immune responses to influenza A/H1N1 originates from activated memory B cells. The aim of this study was to identify baseline, early and late blood transcriptional signatures (in peripheral blood mononuclear cells/PBMCs) associated with memory B cell response following influenza vaccination.

METHODS

We used pre- and post-vaccination mRNA-Seq transcriptional profiling on samples from 159 subjects (50-74years old) following receipt of seasonal trivalent influenza vaccine containing the A/California/7/2009/H1N1-like virus, and penalized regression modeling to identify associations with influenza A/H1N1-specific memory B cell ELISPOT response after vaccination.

RESULTS

Genesets and genes (p-value range 7.92E(-08) to 0.00018, q-value range 0.00019-0.039) demonstrating significant associations (of gene expression levels) with memory B cell response suggest the importance of metabolic (cholesterol and lipid metabolism-related), cell migration/adhesion, MAP kinase, NF-kB cell signaling (chemokine/cytokine signaling) and transcriptional regulation gene signatures in the development of memory B cell response after influenza vaccination.

CONCLUSION

Through an unbiased transcriptome-wide profiling approach, our study identified signatures of memory B cell response following influenza vaccination, highlighting the underappreciated role of metabolic changes (among the other immune function-related events) in the regulation of influenza vaccine-induced immune memory.

Reasons given for not receiving an influenza vaccination, 2011-12 influenza season, United States

BACKGROUND

Influenza vaccination coverage in the United States remains below national targets and racial/ethnic differences persist.

OBJECTIVES

To gain insights into potential strategies for improving influenza vaccination by examining reasons given for not receiving an influenza vaccination during the 2011-12 influenza season.

METHODS

Data from the National Flu Survey were analyzed for the 2011-12 influenza season. Tests of association between reasons for non-vaccination and demographic variables were conducted using Wald chi-square tests. Multivariable logistic regression analyses were used to determine variables independently associated with each reason for non-vaccination.

RESULTS

For adults and children, there were no racial/ethnic differences in the overall most frequent reason for non-vaccination: "unlikely to get very sick from the flu". Regarding adults, there were racial/ethnic differences in seven of the twelve reasons for non-vaccination in bivariate analyses, but only three remained significant in the multivariable models. Most notable of these was that blacks (40.9%) were more likely than Hispanics (27.0%), whites (25.2%), and adults of other/multiple races (21.2%) to report concerns about getting the flu from the vaccination and blacks (39.8%) were more likely than whites (28.4%) and adults of other/multiple races (29.3%) to report concerns about side effects from the vaccine. Regarding children, there were racial/ethnic differences for three of the reasons for non-vaccination, and these remained significant in the multivariable models. The most noteworthy of these was that more black (44.4%) than white (24.0%) and other/multiple race (19.0%) parents had concerns about their child getting the flu from the vaccination. Other demographic variables (age, gender income, MSA for adults and age and income for children) were also associated with reasons for non-vaccination based on the multivariable models.

CONCLUSIONS

There are racial/ethnic group differences in reasons for not receiving an influenza vaccination; recognition of these differences should guide the choice of interventions to increase vaccination rates.

A Case of Severe Pseudomembranous Tracheobronchitis Complicated by Co-infection of Influenza A (H1N1) and Staphylococcus aureus in an Immunocompetent Patient

Although influenza A (H1N1) virus leads to self-limiting illness, co-infection with bacteria may result in cases of severe respiratory failure due to inflammation and necrosis of intra-airway, as pseudomembranous tracheobronchitis. Pseudomembranous tracheobronchitis is usually developed in immunocompromised patients, but it can also occur in immunocompetent patients on a very rare basis. We report a case of pseudomembranous tracheobronchitis complicated by co-infection of inflenaza A and Staphylococcus aureus, causing acute respiratory failure in immunocompetent patients.

Influenza Vaccination Coverage and Its Associated Factors among North Korean Defectors Living in the Republic of Korea

This study aimed to examine influenza vaccination coverage of North Korean defectors (NKD) in the Republic of Korea (Korea) and explore the factors affected the vaccination coverage. Total 378 NKD were analyzed. Four Korean control subjects were randomly matched by age and gender from the Korea National Health and Nutrition Examination Survey V (n = 1,500). The adjusted vaccination coverage revealed no statistical difference between the defectors group and indigenous group (29.1% vs. 29.5%, P = 0.915). In the aged under 50 group, the vaccination coverage of NKD was higher than that of Korean natives (37.8% vs. 25.8%, P = 0.016). However in the aged 50 yr and over group, the vaccination coverage of North Korean defectors was lower than that of the natives (28.0% vs. 37.6%, P = 0.189). Even the gap was wider in the aged 65 yr and over group (36.4% vs. 77.8%, P = 0.007). Gender and medical check-up experience within 2 yr showed association with the vaccination coverage of NKD. Influenza vaccination coverage of aged defectors' group (aged 50 yr and over) was lower than indigenous people though overall vaccination coverage was similar. Further efforts to increase influenza vaccination coverage of this group are needed.

Increasing uptake of live attenuated influenza vaccine among children in the United States, 2008-2014

The Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for all persons in the United States aged ≥6 months. On June 25, 2014, ACIP preferentially recommended live attenuated influenza vaccine (LAIV) for healthy children aged 2-8 years. Little is known about national LAIV uptake. To determine uptake of LAIV relative to inactivated influenza vaccine, we analyzed vaccination records from six immunization information system sentinel sites (approximately 10% of US population). LAIV usage increased over time in all sites. Among children 2-8 years of age vaccinated for influenza, exclusive LAIV usage in the collective sentinel site area increased from 20.1% (2008-09 season) to 38.0% (2013-14). During 2013-14, at least half of vaccinated children received LAIV in Minnesota (50.0%) and North Dakota (55.5%). Increasing LAIV usage suggests formulation acceptability, and this preexisting trend offers a favorable context for implementation of ACIP's preferential recommendation.

The association between influenza treatment and hospitalization-associated outcomes among Korean children with laboratory-confirmed influenza

There are limited data evaluating the relationship between influenza treatment and hospitalization duration. Our purpose assessed the association between different treatments and hospital stay among Korean pediatric influenza patients. Total 770 children ≤ 15 yr-of-age hospitalized with community-acquired laboratory-confirmed influenza at three large urban tertiary care hospitals were identified through a retrospective medical chart review. Demographic, clinical, and cost data were extracted and a multivariable linear regression model was used to assess the associations between influenza treatment types and hospital stay. Overall, there were 81% of the patients hospitalized with laboratory-confirmed influenza who received antibiotic monotherapy whereas only 4% of the patients received oseltamivir monotherapy. The mean treatment-related charges for hospitalizations treated with antibiotics, alone or with oseltamivir, were significantly higher than those treated with oseltamivir-only (P < 0.001). Influenza patients treated with antibiotics-only and antibiotics/oseltamivir combination therapy showed 44.9% and 28.2%, respectively, longer duration of hospitalization compared to those treated with oseltamivir-only. Patients treated with antibiotics, alone or combined with oseltamivir, were associated with longer hospitalization and significantly higher medical charges, compared to patients treated with oseltamivir alone. In Korea, there is a need for more judicious use of antibiotics, appropriate use of influenza rapid testing.

Influenza vaccines: unmet needs and recent developments

Influenza is a worldwide public health concern. Since the introduction of trivalent influenza vaccine in 1978, vaccination has been the primary means of prevention and control of influenza. Current influenza vaccines have moderate efficacy, good safety, and acceptable tolerability; however, they have unsatisfactory efficacy in older adults, are dependent on egg supply for production, and are time-consuming to manufacture. This review outlines the unmet medical needs of current influenza vaccines. Recent developments in influenza vaccines are also described.

Influenza surveillance using electronic health records in the American Indian and Alaska Native population

OBJECTIVE

Increasing use of electronic health records (EHRs) provides new opportunities for public health surveillance. During the 2009 influenza A (H1N1) virus pandemic, we developed a new EHR-based influenza-like illness (ILI) surveillance system designed to be resource sparing, rapidly scalable, and flexible. 4 weeks after the first pandemic case, ILI data from Indian Health Service (IHS) facilities were being analyzed.

MATERIALS AND METHODS

The system defines ILI as a patient visit containing either an influenza-specific International Classification of Disease, V.9 (ICD-9) code or one or more of 24 ILI-related ICD-9 codes plus a documented temperature ≥100°F. EHR-based data are uploaded nightly. To validate results, ILI visits identified by the new system were compared to ILI visits found by medical record review, and the new system's results were compared with those of the traditional US ILI Surveillance Network.

RESULTS

The system monitored ILI activity at an average of 60% of the 269 IHS electronic health databases. EHR-based surveillance detected ILI visits with a sensitivity of 96.4% and a specificity of 97.8% based on chart review (N=2375) of visits at two facilities in September 2009. At the peak of the pandemic (week 41, October 17, 2009), the median time from an ILI visit to data transmission was 6 days, with a mode of 1 day.

DISCUSSION

EHR-based ILI surveillance was accurate, timely, occurred at the majority of IHS facilities nationwide, and provided useful information for decision makers. EHRs thus offer the opportunity to transform public health surveillance.

Clinical Predictors of Influenza in Young Children: The Limitations of "Influenza-Like Illness"

BACKGROUND

Influenza-like illness (ILI) definitions have been infrequently studied in young children. Despite this, clinical definitions of ILI play an important role in influenza surveillance. This study aims to identify clinical predictors of influenza infection in children ≤5 years old from which age-specific ILI definitions are then constructed.

METHODS

Children aged 6-59 months with a history of fever and acute respiratory symptoms were recruited in the Western Australia Influenza Vaccine Effectiveness (WAIVE) Study. Clinical data and per-nasal specimens were obtained from all children. Logistic regression identified significant predictors of influenza infection. Different ILI definitions were compared for diagnostic accuracy.

RESULTS

Children were recruited from 2 winter influenza seasons (2008-2009; n = 944). Of 919 eligible children, 179 (19.5%) had laboratory-confirmed influenza infection. Predictors of infection included increasing age, lack of influenza vaccination, lower birth weight, fever, cough, and absence of wheeze. An ILI definition comprising fever ≥38°C, cough, and no wheeze had 58% sensitivity (95% confidence interval [CI], 50-66), 60% specificity (95% CI, 56-64), 26% positive predictive value (95% CI, 21-31), and 86% negative predictive value (95% CI, 82-89). The addition of other symptoms or higher fever thresholds to ILI definition had little impact. The Centers for Disease Control and Prevention definition of ILI (presence of fever [≥37.8°C] and cough and/or sore throat) was sensitive (92%; 95% CI, 86-95), yet lacked specificity (10%; 95% CI, 8-13) in this population.

CONCLUSIONS

Influenza-like illness is a poor predictor of laboratory-confirmed influenza infection in young children but can be improved using age-specific data. Incorporating age-specific ILI definitions and/or diagnostic testing into influenza surveillance systems will improve the accuracy of epidemiological data.

Post-influenza pneumonia caused by the USA300 community-associated methicillin-resistant Staphylococcus aureus in Korea

Panton-Valentine leukocidin (PVL)-positive USA300 clone has been the most successful community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) clone spreading in North America. In contrast, PVL-negative ST72-CA-MRSA has been predominant in Korea, and there has been no report of infections by the USA300 strain except only one case report of perianal infection. Here, we describe the first case of pneumonia caused by the USA300 strain following pandemic influenza A (H1N1) in Korea. A 50-year-old man was admitted with fever and cough and chest radiograph showed pneumonic consolidation at the right lower lung zone. He received a ventilator support because of respiratory failure. PCR for pandemic influenza A (H1N1) in nasopharyngeal swab was positive, and culture of sputum and endotracheal aspirate grew MRSA. Typing of the isolate revealed that it was PVL-positive, ST 8-MRSA-SCCmec type IV. The analysis of the PFGE patterns showed that this isolate was the same pulsotype as the USA300 strain.

Immunogenicity and safety of trivalent inactivated influenza vaccine: a randomized, double-blind, multi-center, phase 3 clinical trial in a vaccine-limited country

Influenza vaccines are the primary method for controlling influenza and its complications. This study was conducted as a phase 3, randomized, double-blind, controlled, multi-center trial at seven university hospitals to evaluate the immunogenicity and safety of an inactivated, split, trivalent influenza vaccine (GC501, Green Cross Corporation, Yongin, Korea), which was newly manufactured in Korea in 2008. Between September 21 and 26, a total of 329 healthy subjects were recruited for the immunogenicity analysis, while 976 subjects were enrolled for the safety analysis. The GC501 vaccine met both FDA and EMEA criteria with ≥ 80% of subjects achieving post-vaccination titers ≥ 40 for all three subtypes, even in the elderly. The vaccine was well tolerated with only mild systemic and local adverse events. In summary, GC501 showed excellent immunogenicity and a good safety profile in both young adults and the elderly. The licensure of GC501 might be an important basis in preparation for the future influenza pandemic.

The spread of pandemic H1N1 2009 by age and region and the comparison among monitoring tools

This report describes the pattern of the spread of the pandemic H1N1 2009 and compares 3 monitoring tools until the 57th week or January 31, 2010. The 1st week was from December 28th, 2008 to January 3rd, 2009. A total of 740,835 patients were reported to be infected with pandemic H1N1 2009 and 225 patients were reported to have died of pandemic H1N1 2009. The number of patients aged from 7 to 12 was the largest (183,363 patients in total) but the virus spread and then was suppressed most quickly among the children between 13 and 18. The region-determinant incidence of patients showed diverse patterns according to regions. The peak of the ILI per thousand was at the 45th week, the number of antiviral prescriptions reached its peak at the 44th week, and the peak based on reported patients was the 46th week. As of February 3 2010, the outbreak passed through the peak and has gradually subsided. Now it is time for the government and the academic world to review this outbreak, efficacy of vaccination, and further preparation and response for the next pandemic.