Influenza- and respiratory syncytial virus-associated mortality and hospitalisations

Modulation of the host immune response by respiratory syncytial virus proteins

Respiratory syncytial virus (RSV) causes severe respiratory disease in both the very young and the elderly. Nearly all individuals become infected in early childhood, and reinfections with the virus are common throughout life. Despite its clinical impact, there remains no licensed RSV vaccine. RSV infection in the respiratory tract induces an inflammatory response by the host to facilitate efficient clearance of the virus. However, the host immune response also contributes to the respiratory disease observed following an RSV infection. RSV has evolved several mechanisms to evade the host immune response and promote virus replication through interactions between RSV proteins and immune components. In contrast, some RSV proteins also play critical roles in activating, rather than suppressing, host immunity. In this review, we discuss the interactions between individual RSV proteins and host factors that modulate the immune response and the implications of these interactions for the course of an RSV infection.

Post-extubation stridor in Respiratory Syncytial Virus bronchiolitis: Is there a role for prophylactic dexamethasone?

Aim

The purpose of this study was to determine the incidence of reintubation due to upper airway obstruction in a homogeneous group of ventilated infants with Respiratory Syncytial Virus bronchiolitis. Our secondary objective was to determine whether prophylactic administration of dexamethasone prior to extubation was associated with decreased risk of reintubation.

Methods

This retrospective observational study in two Pediatric Intensive Care Units in 2 university hospitals in The Netherlands included two hundred patients younger than 13 months admitted with respiratory insufficiency caused by Respiratory Syncytial Virus bronchiolitis, requiring invasive mechanical ventilation. A logistic regression analysis with propensity score method was used to adjust for possible confounding.

Results

Reintubation due to post-extubation stridor occurred in 17 (8.5%) of 200 patients. After propensity score matching, administration of dexamethasone prior to extubation was associated with a significantly (p = 0.0011) decreased risk of reintubation due to post-extubation stridor compared to patients not receiving prophylactic dexamethasone (absolute risk reduction 13%, 95% CI 5.3–21%).

Conclusion

Reintubation due to post-extubation stridor is an important complication of ventilation for Respiratory Syncytial Virus bronchiolitis. Dexamethasone administered prior to extubation probably reduces the risk of post-extubation stridor necessitating reintubation in these infants. The results of this study support initiation of a placebo-controlled trial to confirm the beneficial effect of prophylactic dexamethasone.

Development of Seasonal Influenza Vaccination Recommendations: Relevance and Influence of the Evidence on the Decision-Making Process in France and the Netherlands

BACKGROUND

Target groups for seasonal influenza vaccination are defined at the country level and are based on several factors. However, little is known about the national decision-making procedures.

OBJECTIVE

The purpose of this study was to compare the evidence used for the development of recommendations and its impact on the choice of target groups in France and the Netherlands.

METHODS

A preliminary documentary analysis identified institutions to include in the assessment: governmental authorities, research institutions, associations, and manufacturers. At least one expert from each group was invited to our study. Thirty-three semi-structured interviews were conducted in 2013 (16 France, 17 the Netherlands). We used NVivo10® to perform a thematic content analysis.

RESULTS

Clinical/epidemiological studies were the evidence most used in both countries. Economic models were increasingly being used; these had greater influence on the decision making in the Netherlands than in France, probably because of the presence of a modeler. Generally, the quality of the evidence used was poor, although no systematic use of standard protocol for its assessment was observed. A general protocol was sometimes used in France; however, the personal judgment of the experts was crucial for the assessment in both countries.

CONCLUSIONS

There were differences in the target groups, for example, pregnant women, recommended only in France. France and the Netherlands use similar evidence for developing vaccination recommendations, although different decisions are sometimes made regarding target groups. This could be associated with the lack of systematic standard appraisals, increasing the influence of the experts' judgment on decision making. The development of standards for the appraisal of evidence is recommended.

Invasive Pneumococcal Disease 3 Years after Introduction of 10-Valent Pneumococcal Conjugate Vaccine, the Netherlands

Three years after a 7-valent pneumococcal conjugate vaccine was replaced by a 10-valent pneumococcal conjugate vaccine in the Netherlands, we observed a decrease in incidence of invasive pneumococcal disease caused by Streptococcus pneumoniae serotypes 1, 5, and 7F. Our data do not support or exclude cross-protection against serotype 19A.

The success of microneedle-mediated vaccine delivery into skin

Microneedles (MNs) are designed to specifically target the outermost, skin barrier layer, the stratum corneum, creating transient pathways for minimally invasive transcutaneous delivery. It is reported that MNs can facilitate delivery without stimulating the pain receptors or damaging blood vessels that lie beneath, thus being perceived as painless and associated with reduced bleeding. This immunocompetence of the skin, coupled with its ease of access, makes this organ an attractive vaccination site. The purpose of this review was to collate primary scientific literature pertaining to MN-mediated in vivo vaccination programmes. A total of 62 original research articles are presented, compiling vaccination strategies in 6 different models (mouse, rat, guinea pig, rabbit, pig, macaque and human). Vaccines tested span a wide range of viral, bacterial and protozoan pathogens and includes 7 of the 13 vaccine-preventable diseases, as defined by the WHO. This review highlights the paucity of available clinical trial data. MN-delivered vaccines have demonstrated safety and immunogenicity in pre-clinical models and boast desirable attributes such as painless administration, thermostability, dose-sparing capacity and the potential for self-administration. These advantages should contribute to enhanced global vaccine access.

Prediction model of RSV-hospitalization in late preterm infants: An update and validation study

BACKGROUND

New vaccines and RSV therapeutics have been developed in the past decade. With approval of these new pharmaceuticals on the horizon, new challenges lie ahead in selecting the appropriate target population. We aimed to improve a previously published prediction model for prediction of RSV-hospitalization within the first year of life.

METHODS

Two consecutive prospective multicenter birth cohort studies were performed from June 2008 until February 2015. The first cohort (RISK-I, n=2524, 2008-2011) was used to update the existing model. The updated model was subsequently validated in the RISK-II cohort (n=1564, 2011-2015). We used the TRIPOD criteria for transparent reporting.

RESULTS

181 infants (n=127 in RISK-I, n=54 in RISK-II) were hospitalized for RSV within their first year of life. The updated model included the following predictors; day care attendance and/or siblings (OR: 5.3; 95% CI 2.8-10.1), birth between Aug. 14th and Dec. 1st (OR: 2.4; 1.8-3.2), neonatal respiratory support (OR 2.2; 1.6-3.0), breastfeeding ≤4 months (OR 1.6; 1.2-2.2) and maternal atopic constitution (OR 1.5; 1.1-2.1). The updated models' discrimination was superior to the original model in the RISK-II cohort (AUROC 0.72 95% CI 0.65-0.78 versus AUROC 0.66, 95% CI 0.60-0.73, respectively). The updated model was translated into a simple nomogram to be able to distinguish infants with high versus low risk of RSV-hospitalization.

CONCLUSION

We developed and validated a clinical prediction model to be able to predict RSV-hospitalization in preterm infants born within 32-35 weeks gestational age. A simple nomogram was developed to target RSV therapeutics to those children who will benefit the most.

Detecting respiratory viral RNA using expanded genetic alphabets and self-avoiding DNA

Nucleic acid (NA)-targeted tests detect and quantify viral DNA and RNA (collectively xNA) to support epidemiological surveillance and, in individual patients, to guide therapy. They commonly use polymerase chain reaction (PCR) and reverse transcription PCR. Although these all have rapid turnaround, they are expensive to run. Multiplexing would allow their cost to be spread over multiple targets, but often only with lower sensitivity and accuracy, noise, false positives, and false negatives; these arise by interactions between the multiple nucleic acid primers and probes in a multiplexed kit. Here we offer a multiplexed assay for a panel of respiratory viruses that mitigates these problems by combining several nucleic acid analogs from the emerging field of synthetic biology: (i) self-avoiding molecular recognition systems (SAMRSs), which facilitate multiplexing, and (ii) artificially expanded genetic information systems (AEGISs), which enable low-noise PCR. These are supplemented by “transliteration” technology, which converts standard nucleotides in a target to AEGIS nucleotides in a product, improving hybridization. The combination supports a multiplexed Luminex-based respiratory panel that potentially differentiates influenza viruses A and B, respiratory syncytial virus, severe acute respiratory syndrome coronavirus (SARS), and Middle East respiratory syndrome (MERS) coronavirus, detecting as few as 10 MERS virions in a 20-μl sample.

Hospitalizations associated with influenza and respiratory syncytial virus among patients attending a network of private hospitals in South Africa, 2007-2012

Background

Influenza and respiratory syncytial virus (RSV) infection are common causes of lower respiratory tract illness. Data on their burden in low and middle-income settings and from Africa are scarce. We aimed to estimate age-specific rates of hospitalization attributable to influenza and RSV among patients attending private hospitals in South Africa during 2007–2012.

Methods

We estimated annual age-specific rates of influenza- and RSV-associated hospitalization (that is respiratory hospitalizations likely due to influenza or RSV infection) by applying regression models to monthly administrative hospitalization data from a national private hospital group, using influenza and RSV surveillance data as covariates.

Results

Estimated mean hospitalization rates associated with seasonal influenza were 75 (95% confidence interval (CI), 41–108) and 3 (95% CI, 2–5) per 100,000 person-years for all-respiratory and all-circulatory causes, respectively. Children <1 year and adults ≥75 years were the most affected, with influenza-associated all-respiratory hospitalization rates estimated at 255 (95% CI, 143–358) and 380 (95% CI, 227–506) per 100,000 person-years, respectively. Excess all-circulatory hospitalizations associated with seasonal influenza were only observed in adults ≥65 years. Annual hospitalization rates associated with RSV averaged an estimate of 223 (95% CI, 128–317) per 100,000 person-years for all-respiratory causes. Among children <1 year, RSV-associated all-respiratory hospitalization rate of 7,601 (95% CI, 4,312-10,817) per 100,000 person-years was estimated.

Conclusions

Influenza and RSV substantially contributed to hospitalizations over the study period.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-014-0694-x) contains supplementary material, which is available to authorized users.

Clinical characteristics and risk factors of severe respiratory syncytial virus-associated acute lower respiratory tract infections in hospitalized infants

BACKGROUND

To investigate the clinical characteristics and analyze risk factors for severe respiratory syncytial virus (RSV) infection in hospitalized infants with acute lower respiratory tract infections (ALRIs).

METHODS

A retrospective review of the medical records of infants with RSV-associated ALRIs between March 1st, 2011 and February 29th, 2012 was conducted. Subjects were followed up over the phone or by outpatient visit six and twelve months after discharge.

RESULTS

Among 913 RSV-associated ALRIs infants, 288 (31.5%) had severe infections, which accounted for 4.2% of hospitalized children. The hospital RSV mortality rate was 1.0%. The proportions of cases with tachypnea, apnea, cyanosis, and fine rales were significantly higher in the severe ALRIs group (all P<0.001). Multivariate logistic regression showed that low-birth-weight [1.698 (1.028-2.805)], age less than 3 months old [3.385 (2.174-5.271)], congenital heart disease [1.667 (1.149-2.418)], bronchopulmonary dysplasia [8.505 (1.731-41.780)], and airway abnormalities [2.246 (1.008-5.005)] were independent risk factors for severe ALRIs. The incidence of bronchitis, pneumonia and readmission in the severe group was significantly higher than that of the non-severe group during the one-year follow-up (all P<0.001).

CONCLUSIONS

Younger age, low birth weight and underlying disease are associated with severe RSVassociated ALRIs. Furthermore, severe RSV infections may be associated with a higher frequency of subsequent bronchitis, pneumonia and re-hospitalization in the following year.

Comparison of three commercial RT-PCR systems for the detection of respiratory viruses

BACKGROUND

Due to the insensitivity of rapid tests for respiratory viruses, nucleic acid amplification tests are quickly becoming the standard of care.

OBJECTIVES AND STUDY DESIGN

The performance of the FilmArray Respiratory Panel (RP) and Verigene RV+ (RV+) were compared in a retrospective analysis of 89 clinical specimens previously determined to be positive for the following viruses by our test of record, Prodesse (Pro): influenza A (29, FluA), influenza B (13, FluB), respiratory syncytial virus (12, RSV), human metapneumovirus (10, hMPV), parainfluenza (14, PIV), and adenovirus (10, AdV). Samples positive for influenza A, B or RSV were tested by both methods, while the remainder were tested by RP only. True positives were defined as positive by two or more assays.

RESULTS

Limit of detection (LOD) analyses demonstrated Pro had the lowest LOD for all FluA strains tested, PIV1, PIV2 and AdV; RV+ had the lowest LOD for FluB; and RP had the lowest LOD for RSV, PIV3 and hMPV. Of the 55 samples tested by RV+, all 54 true positive samples were positive by RV+. Of the 89 samples tested by RP, 85 of the 88 true positive samples were positive by RP. From these results, the overall sensitivities for influenza A, B and RSV were 100% and 98% for RV+ and RP, respectively. The overall sensitivity of RP for all viruses was 97%.

CONCLUSIONS

In summary, these systems demonstrated excellent performance. Furthermore, each system has benefits which will ensure they will all have a niche in a clinical laboratory.

Annual public health and economic benefits of seasonal influenza vaccination: a European estimate

BACKGROUND

Vaccination is currently the most effective means of preventing influenza infection. Yet evidence of vaccine performance, and the impact and value of seasonal influenza vaccination across risk groups and between seasons, continue to generate much discussion. Moreover, vaccination coverage is below recommended levels.

METHODS

A model was generated to assess the annual public health benefits and economic importance of influenza vaccination in 5 WHO recommended vaccination target groups (children 6 - 23 months of age; persons with underlying chronic health conditions; pregnant women; health care workers; and, the elderly, 65 years of age) in 27 countries of the European Union. Model estimations were based on standard calculation methods, conservative assumptions, age-based and country-specific data.

RESULTS

Out of approximately 180 million Europeans for whom influenza vaccination is recommended, only about 80 million persons are vaccinated. Seasonal influenza vaccination currently prevents an annual average of between 1.6 million and 2.1 million cases of influenza, 45,300 to 65,600 hospitalizations, and 25,200 to 37,200 deaths. To reach the 75% vaccination coverage target set by the EU Council Recommendation in 2009, an additional 57.4 million person would need to be vaccinated in the elderly and other risk groups. By achieving the 75% target rate set in EU-27 countries, average annual influenza- related events averted would increase from current levels to an additional +1.6 to +1.7 million cases, +23,800 to +31,400 hospitalization, +9,800 to +14,300 deaths, +678,500 to +767,800 physician visits, and +883,800 to +1,015,100 lost days of work yearly. Influenza-related costs averted because of vaccination would increase by an additional + €190 to + €226 million yearly, in vaccination target groups.

CONCLUSIONS

Full implementation of current influenza vaccination recommendations of 75% vaccination coverage rate (VCR) in Europe by the 2014-2015 influenza season could immediately reduce an important public health and economic burden.

Antigenically intact hemagglutinin in circulating avian and swine influenza viruses and potential for H3N2 pandemic

The 2009 swine-origin H1N1 influenza, though antigenically novel to the population at the time, was antigenically similar to the 1918 H1N1 pandemic influenza, and consequently was considered to be “archived” in the swine species before reemerging in humans. Given that the H3N2 is another subtype that currently circulates in the human population and is high on WHO pandemic preparedness list, we assessed the likelihood of reemergence of H3N2 from a non-human host. Using HA sequence features relevant to immune recognition, receptor binding and transmission we have identified several recent H3 strains in avian and swine that present hallmarks of a reemerging virus. IgG polyclonal raised in rabbit with recent seasonal vaccine H3 fail to recognize these swine H3 strains suggesting that existing vaccines may not be effective in protecting against these strains. Vaccine strategies can mitigate risks associated with a potential H3N2 pandemic in humans.

Impaired immune response to vaccination against infection with human respiratory syncytial virus at advanced age

Elderly humans are prone to severe infection with human respiratory syncytial virus (HRSV). The aging of today's human population warrants the development of protective vaccination strategies aimed specifically at the elderly. This may require special approaches due to deteriorating immune function. To design and test vaccination strategies tailored to the elderly population, we need to understand the host response to HRSV vaccination and infection at old age. Moreover, the preclinical need for testing of candidate vaccines requires translational models resembling susceptibility to the (unadapted) human pathogen. Here, we explored the effects of aging on immunity and protection induced by a model HRSV vaccine candidate in a translational aging model in cotton rats (Sigmodon hispidus) and examined possibilities to optimize vaccination concepts for the elderly. We immunized young and aged cotton rats with a live-attenuated recombinant HRSV vaccine candidate and analyzed the induced immune response to and protection against challenge with HRSV. In old cotton rats, HRSV infection persisted longer, and vaccination induced less protection against infection. Aged animals developed lower levels of vaccine-induced IgG, virus-neutralizing serum antibodies, and IgA in lungs. Moreover, booster responses to HRSV challenge were impaired in animals vaccinated at an older age. However, increased dose and reduced attenuation of vaccine improved protection even in old animals. This study shows that cotton rats provide a model for studying the effects of aging on the immune response to the human respiratory pathogen HRSV and possibilities to optimize vaccine concepts for the elderly.

IMPORTANCE

HRSV infection poses a risk for severe disease in the elderly. The aging of the population warrants increased efforts to prevent disease at old age, whereas HRSV vaccines are only in the developmental phase. The preclinical need for testing of candidate human vaccines requires translational models resembling susceptibility to the natural human virus. Moreover, we need to gain insight into waning immunity at old age, as this is a special concern in vaccine development. In this study, we explored the effect of age on protection and immunity against an experimental HRSV vaccine in aged cotton rats (Sigmodon hispidus), a rodent species that provides a model representing natural susceptibility to human viruses. Older animals generate fewer antibodies upon vaccination and require a higher vaccine dose for protection. Notably, during the early secondary immune response to subsequent HRSV infection, older animals showed less protection and a slower increase of the virus-neutralizing antibody titer.

Broadly neutralizing influenza hemagglutinin stem-specific antibody CR8020 targets residues that are prone to escape due to host selection pressure

Broadly neutralizing antibodies (bNAb) that target a conserved region of a viral antigen hold significant therapeutic promise. CR8020 is a bNAb that targets the stem region of influenza A virus (IAV) hemagglutinin (HA). CR8020 is currently being evaluated for prophylactic use against group 2 IAVs in phase II studies. Structural and computational analyses reported here indicate that CR8020 targets HA residues that are prone to antigenic drift and host selection pressure. Critically, CR8020 escape mutation is seen in certain H7N9 viruses from recent outbreaks. Furthermore, the ability of the bNAb Fc region to effectively engage activating Fcγ receptors (FCγR) is essential for antibody efficacy. In this regard, our data indicate that the membrane could sterically hinder the formation of HA-CR8020-FcγRIIa/HA-IgG-FcγRIIIa ternary complexes. Altogether, our analyses suggest that epitope mutability and accessibility to immune complex assembly are important attributes to consider when evaluating bNAb candidates for clinical development.

Respiratory syncytial virus--a comprehensive review

Respiratory syncytial virus (RSV) is amongst the most important pathogenic infections of childhood and is associated with significant morbidity and mortality. Although there have been extensive studies of epidemiology, clinical manifestations, diagnostic techniques, animal models and the immunobiology of infection, there is not yet a convincing and safe vaccine available. The major histopathologic characteristics of RSV infection are acute bronchiolitis, mucosal and submucosal edema, and luminal occlusion by cellular debris of sloughed epithelial cells mixed with macrophages, strands of fibrin, and some mucin. There is a single RSV serotype with two major antigenic subgroups, A and B. Strains of both subtypes often co-circulate, but usually one subtype predominates. In temperate climates, RSV infections reflect a distinct seasonality with onset in late fall or early winter. It is believed that most children will experience at least one RSV infection by the age of 2 years. There are several key animal models of RSV. These include a model in mice and, more importantly, a bovine model; the latter reflects distinct similarity to the human disease. Importantly, the prevalence of asthma is significantly higher amongst children who are hospitalized with RSV in infancy or early childhood. However, there have been only limited investigations of candidate genes that have the potential to explain this increase in susceptibility. An atopic predisposition appears to predispose to subsequent development of asthma and it is likely that subsequent development of asthma is secondary to the pathogenic inflammatory response involving cytokines, chemokines and their cognate receptors. Numerous approaches to the development of RSV vaccines are being evaluated, as are the use of newer antiviral agents to mitigate disease. There is also significant attention being placed on the potential impact of co-infection and defining the natural history of RSV. Clearly, more research is required to define the relationships between RSV bronchiolitis, other viral induced inflammatory responses, and asthma.

RSV vaccine in development: assessing the potential cost-effectiveness in the Dutch elderly population

OBJECTIVES

Respiratory syncytial virus (RSV) is increasingly recognized as an important cause of morbidity, mortality and health-care utilization in the elderly population. A theoretical model was built to assess the levels of vaccine effectiveness and vaccine costs for which a hypothetical RSV-vaccine for Dutch elderly could be cost-effective.

METHODS

Different vaccination strategies were evaluated by changing the levels of vaccine effectiveness and the willingness to pay per quality-adjusted life year gained (QALY). Outcome measures included direct medical costs, QALYs, life years gained, incremental cost-effectiveness ratios (ICERs) and the maximum total vaccination costs per individual (i.e. (vaccine price+administration costs)×nr of doses) while remaining cost-effective.

RESULTS

Using base-case assumptions, it was estimated that vaccination of all persons 60 years and older would prevent 3402GP visits, 2989 antibiotic prescriptions, 535 hospitalizations and 249 deaths and would cost €73,261 per QALY, for a vaccine effectiveness of 70%. Vaccinating only the high risk population of 60 years and older would reduce the estimates to 2042GP visits, 2009 antibiotic prescriptions, 179 hospitalizations and 209 deaths and this reduced the cost per QALY to €34,796 per QALY. Using the same assumptions, the maximum total vaccination costs per individual ranged from €26 when vaccinating all persons 60 and older to €68 when vaccinating only persons aged 85 and above, using a willingness to pay threshold of €50,000 per QALY. For the high risk population aged 60 years and older the estimated maximum total vaccination costs ranged from €52 to €99.

CONCLUSION

Vaccination of Dutch elderly against RSV was found cost-effective for several scenarios. As expected, vaccination is more likely to be cost-effective when only including persons who are at increased risk for contracting RSV or the potential complications of RSV. This theoretical study shows that based on the disease burden in the Dutch population aged 60yrs and older there is potential to develop a vaccine that might be considered cost-effective in the Netherlands.

Other viral pneumonias: coronavirus, respiratory syncytial virus, adenovirus, hantavirus

Severe viral pneumonia is an increasing problem among adults. The incidence and number of viruses known to cause pneumonia and respiratory failure have also expanded in recent years. This article provides an overview of severe respiratory disease caused by coronavirus, respiratory syncytial virus, adenovirus, and hantavirus. These emerging pathogens are easily overlooked and timely diagnosis requires a high index of suspicion and confirmation by molecular testing. Management of individual cases is mainly supportive and requires institution of appropriate infection control measures. Vaccines and effective therapeutics for these potentially devastating respiratory viruses are urgently required.

High morbidity and mortality in adults hospitalized for respiratory syncytial virus infections

BACKGROUND

Better understanding of complications and outcomes of adults hospitalized with respiratory syncytial virus (RSV) infection is necessary.

METHODS

A retrospective cohort study was conducted on all adults (≥ 18 years) admitted to 3 acute care general hospitals in Hong Kong with virologically confirmed RSV infection during 2009-2011 (N = 607). Adults hospitalized for seasonal influenza during the period were used for comparison (n = 547). Both infections were prospectively diagnosed following a standard protocol. Independent reviews of chest radiographs were performed by radiologists. Main outcome measures were all-cause death, respiratory failure requiring ventilatory support, and hospitalization duration. Cox proportional hazards models were used for analyses.

RESULTS

The mean age of RSV patients was 75 (SD, 16) years; 87% had underlying conditions. Lower respiratory and cardiovascular complications were diagnosed in 71.9% (pneumonia, 42.3%; acute bronchitis, 21.9%; chronic obstructive pulmonary disease/asthma exacerbation, 27.3%) and 14.3% of patients, respectively; 12.5% had bacterial superinfections. Supplemental oxygen and ventilatory support were required in 67.9% and 11.1%, respectively. Crude all-cause mortality was 9.1% and 11.9% within 30 days and 60 days, respectively; mean length of stay of survivors was 12 (SD, 13) days. Advanced age, radiographic pneumonia, requirement for ventilation, bacterial superinfection, and elevated urea level and white blood cell count were independently associated with poorer survival. Systemic corticosteroid use was associated with longer hospitalization and secondary infections. The overall outcomes of survival and length of stay were not significantly different from those in influenza.

CONCLUSIONS

RSV can cause severe lower respiratory complications in older adults, resulting in respiratory failure, prolonged hospitalization, and high mortality similar to seasonal influenza. Corticosteroids did not seem to improve outcomes. The unmet need for antiviral therapy and vaccination against RSV in adults should be promptly addressed.

The impact of influenza and respiratory syncytial virus on hospitalizations for lower respiratory tract infections in young children: Slovenia, 2006-2011

Background

Influenza and respiratory syncytial viruses (RSV) are important viral pathogens in childhood.

Objectives

Our aim was to estimate the effect of influenza and RSV on excess hospitalizations for acute lower respiratory tract infections (ALRTI) in children aged ≤5.

Methods

Retrospective, population‐based study was performed for five seasons (2006–2011). Slovenian national hospital discharge data and surveillance data were used to estimate the effect of influenza and/or RSV on ALRTI hospitalizations (acute bronchiolitis, pneumonia, and acute bronchitis) using rate difference method.

Results

An excess was observed in average weekly ALRTI hospitalizations per 100 000 among children aged ≤5 in all five seasons during influenza and/or RSV active period. During three seasons, there was higher excess in ALRTI hospitalizations in the period when influenza/RSV cocirculated compared with the RSV period. In pandemic season (2009/2010), the only one without influenza/RSV overlap, excess hospitalization was higher in RSV period. The highest excess of hospitalizations was found among the youngest children (0‐5 months old). In all five seasons, acute bronchiolitis was the most common ALRTI recorded in hospitalized young children.

Conclusions

Respiratory syncytial viruses was leading viral pathogen associated with ALRTI hospitalizations in children aged ≤5. The cocirculation of influenza virus increased the burden of ALRTI hospitalizations especially in seasons with A(H3) predominance.

Eight years of the Great Influenza Survey to monitor influenza-like illness in Flanders

In 2003, an internet-based monitoring system of influenza-like illness (ILI), the Great Influenza Survey (GIS), was initiated in Belgium. For the Flemish part of Belgium, we investigate the representativeness of the GIS population and assess the validity of the survey in terms of ILI incidence during eight influenza seasons (from 2003 through 2011). The validity is investigated by comparing estimated ILI incidences from the GIS with recorded incidences from two other monitoring systems, (i) the Belgian Sentinel Network and (ii) the Google Flu Trends, and by performing a risk factor analysis to investigate whether the risks on acquiring ILI in the GIS population are comparable with results in the literature. A random walk model of first order is used to estimate ILI incidence trends based on the GIS. Good to excellent correspondence is observed between the estimated ILI trends in the GIS and the recorded trends in the Sentinel Network and the Google Flu Trends. The results of the risk factor analysis are in line with the literature. In conclusion, the GIS is a useful additional surveillance network for ILI monitoring in Flanders. The advantages are the speed at which information is available and the fact that data is gathered directly in the community at an individual level.

Assessment of vaccine candidates for persons aged 50 and older: a review

BACKGROUND

The increasing life expectancy in most European countries has resulted in growth of the population 50 and older. This population is more susceptible to infectious diseases because of immunosenescence, co-morbidity and general frailty. Thus, to promote healthy aging, vaccination against vaccine-preventable-diseases could be one strategy. In addition to its possible individual benefits, vaccination may also yield social benefits, such as a lower overall cost of healthcare. Most European countries, however, offer only influenza vaccine although vaccines for pneumococcal disease, herpes zoster, pertussis, and hepatitis A are also available. Our aim is to review the knowledge of these vaccines for persons aged 50 and older and explore the arguments for expanding current vaccination programmes beyond just influenza.

METHODS

The evaluation model of Kimman et al. was used to assess herpes zoster, pneumococcal disease, pertussis and hepatitis A in terms of four domains: pathogen, vaccine, disease outcomes and cost-effectiveness. The sources were Dutch surveillance systems, seroprevalence studies and the international literature.

RESULTS

Herpes zoster, pneumococcal disease and pertussis are prevalent among persons aged 50 and older. Vaccines vary in effectiveness and have mild and self-limiting side effects. Vaccination against pneumococcal disease and pertussis causes adaptation of the responsible pathogen. For pertussis and hepatitis A, the vaccine is not registered specifically for the elderly population. Vaccination against herpes zoster and pertussis could improve quality of life, while vaccination against pneumococcal disease and hepatitis A prevents mortality. However, only vaccination against herpes zoster and pneumococcal disease appear to be cost-effective.

CONCLUSIONS

Vaccination can improve the health of the elderly population. As our review shows, however, the data are too incomplete to accurately judge its potential impact. More research is needed to determine how vaccination can most effectively improve the health of the growing population 50 years and older.

Prospective validation of a prognostic model for respiratory syncytial virus bronchiolitis in late preterm infants: a multicenter birth cohort study

OBJECTIVES

This study aimed to update and validate a prediction rule for respiratory syncytial virus (RSV) hospitalization in preterm infants 33-35 weeks gestational age (WGA).

STUDY DESIGN

The RISK study consisted of 2 multicenter prospective birth cohorts in 41 hospitals. Risk factors were assessed at birth among healthy preterm infants 33-35 WGA. All hospitalizations for respiratory tract infection were screened for proven RSV infection by immunofluorescence or polymerase chain reaction. Multivariate logistic regression analysis was used to update an existing prediction model in the derivation cohort (n = 1,227). In the validation cohort (n = 1,194), predicted versus actual RSV hospitalization rates were compared to determine validity of the model.

RESULTS

RSV hospitalization risk in both cohorts was comparable (5.7% versus 4.9%). In the derivation cohort, a prediction rule to determine probability of RSV hospitalization was developed using 4 predictors: family atopy (OR 1.9; 95%CI, 1.1-3.2), birth period (OR 2.6; 1.6-4.2), breastfeeding (OR 1.7; 1.0-2.7) and siblings or daycare attendance (OR 4.7; 1.7-13.1). The model showed good discrimination (c-statistic 0.703; 0.64-0.76, 0.702 after bootstrapping). External validation showed good discrimination and calibration (c-statistic 0.678; 0.61-0.74).

CONCLUSIONS

Our prospectively validated prediction rule identifies infants at increased RSV hospitalization risk, who may benefit from targeted preventive interventions. This prediction rule can facilitate country-specific, cost-effective use of RSV prophylaxis in late preterm infants.

Latitudinal variations in seasonal activity of influenza and respiratory syncytial virus (RSV): a global comparative review

BACKGROUND

There is limited information on influenza and respiratory syncytial virus (RSV) seasonal patterns in tropical areas, although there is renewed interest in understanding the seasonal drivers of respiratory viruses.

METHODS

We review geographic variations in seasonality of laboratory-confirmed influenza and RSV epidemics in 137 global locations based on literature review and electronic sources. We assessed peak timing and epidemic duration and explored their association with geography and study settings. We fitted time series model to weekly national data available from the WHO influenza surveillance system (FluNet) to further characterize seasonal parameters.

RESULTS

Influenza and RSV activity consistently peaked during winter months in temperate locales, while there was greater diversity in the tropics. Several temperate locations experienced semi-annual influenza activity with peaks occurring in winter and summer. Semi-annual activity was relatively common in tropical areas of Southeast Asia for both viruses. Biennial cycles of RSV activity were identified in Northern Europe. Both viruses exhibited weak latitudinal gradients in the timing of epidemics by hemisphere, with peak timing occurring later in the calendar year with increasing latitude (P<0.03). Time series model applied to influenza data from 85 countries confirmed the presence of latitudinal gradients in timing, duration, seasonal amplitude, and between-year variability of epidemics. Overall, 80% of tropical locations experienced distinct RSV seasons lasting 6 months or less, while the percentage was 50% for influenza.

CONCLUSION

Our review combining literature and electronic data sources suggests that a large fraction of tropical locations experience focused seasons of respiratory virus activity in individual years. Information on seasonal patterns remains limited in large undersampled regions, included Africa and Central America. Future studies should attempt to link the observed latitudinal gradients in seasonality of viral epidemics with climatic and population factors, and explore regional differences in disease transmission dynamics and attack rates.

Clinical and epidemiologic features of respiratory syncytial virus

Since its discovery in 1955, respiratory syncytial virus (RSV) has consistently been noted to be the single most important cause of lower respiratory tract illness in infants <1 year of age. RSV also causes repeat infections and significant disease throughout life. In addition to the young child, persons with compromised immune, pulmonary or cardiac systems, and the elderly have significant risk from infection. Though RSV causes the full spectrum of acute respiratory illnesses, it is most notably associated with signs and symptoms of increased airway resistance manifested as wheezing and, in the young child, diagnosed as bronchiolitis. In temperate climates, RSV occurs as yearly outbreaks usually between late fall and early spring lasting 3-4 months in a community. The timing of outbreaks varies between years and in the same year between regions and even between nearby communities. RSV can be a serious nosocomial pathogen in high risk individuals but nosocomial transmission that can often be prevented with meticulous attention to good infection control practices. High risk groups include the premature infants and persons of any age with compromised cardiac, pulmonary, or immune systems. Risk factors for infection include increased number of children in the household and day care center attendance. There are reasonable estimates of the sizable burden of RSV disease in infants and young children and the elderly but less data on disease in older children, the role of RSV in later reactive airway disease (see chapter by M.T. Lotz et al. , this volume), and RSV-associated mortality in developing countries. The available data on burden of disease suggests there are at least four potential target populations for a vaccine, the young infant, young children >4-6 months of age, pregnant women, and the elderly. A link between infection in the young infant and later reactive airway disease and mortality in developing countries is needed. Each target population has different vaccine safety and efficacy concerns and may warrant a different type of vaccine.

Rotavirus-related hospitalizations are responsible for high seasonal peaks in all-cause pediatric hospitalizations

BACKGROUND

Seasonal rotavirus (RV) epidemics partly overlap with those of other common childhood infections, thereby generating enormous, but poorly quantified, pressure on hospital resources during winter and spring. We assessed RV contribution to seasonal excess in all-cause pediatric hospitalizations and RV hospitalization incidence rate in an observational study.

METHODS

The study was conducted among pediatric wards in 3 general hospitals and 1 pediatric tertiary care center. Numbers of RV hospitalizations were determined from 5-year data on confirmed RV hospitalizations and adjusted for RV underreporting, assessed through active surveillance for acute gastroenteritis during the 2011 RV season. Incidence rate and RV contribution to all-cause hospitalizations were determined on hospital administrative data and population statistics.

RESULTS

RV accounted for 6.2% (95% confidence interval: 5.3-7.1) of all-cause pediatric hospitalizations among general hospitals and 3.1% (95% confidence interval: 2.9-3.3) at the tertiary care center, adjusted for the proportion RV underreporting among gastroenteritis patients (33%) as observed during active surveillance. Among general hospitals, there was a 30% increase in all-cause hospitalizations during the active season of common childhood infections compared with summer months. RV contributed 31% to seasonal excess in all-cause pediatric hospitalizations, representing 12.9% of hospitalizations between January and May. RV hospitalizations incidence rate in the population was 510/100,000 child-years <5 years (95% confidence interval: 420-600).

CONCLUSION

RV is one of the main causes of seasonal peaks in pediatric hospitalizations, and as such contributes significantly to periodic high bed capacity pressures and associated adverse effects. RV vaccination benefits in this respect should be considered in decision-making processes.

Rates of hospitalizations for respiratory syncytial virus, human metapneumovirus, and influenza virus in older adults

BACKGROUND

We performed a prospective study to determine the disease burden of respiratory syncytial virus (RSV) and human metapneumovirus (HMPV) in older adults in comparison with influenza virus.

METHODS

During 3 consecutive winters, we enrolled Davidson County (Nashville, TN) residents aged ≥ 50 years admitted to 1 of 4 hospitals with acute respiratory illness (ARI). Nasal/throat swabs were tested for influenza, RSV, and HMPV with reverse-transcriptase polymerase chain reaction. Hospitalization rates were calculated.

RESULTS

Of 1042 eligible patients, 508 consented to testing. Respiratory syncytial virus was detected in 31 participants (6.1%); HMPV was detected in 23 (4.5%) patients; and influenza was detected in 33 (6.5%) patients. Of those subjects aged ≥ 65 years, 78% received influenza vaccination. Compared with patients with confirmed influenza, patients with RSV were older and more immunocompromised; patients with HMPV were older, had more cardiovascular disease, were more likely to have received the influenza vaccination, and were less likely to report fever than those with influenza. Over 3 years, average annual rates of hospitalization were 15.01, 9.82, and 11.81 per 10,000 county residents due to RSV, HMPV, and influenza, respectively.

CONCLUSIONS

In adults aged ≥ 50 years, hospitalization rates for RSV and HMPV were similar to those associated with influenza.

Mortality attributable to 9 common infections: significant effect of influenza A, respiratory syncytial virus, influenza B, norovirus, and parainfluenza in elderly persons

BACKGROUND

Because there may be substantial hidden mortality caused by common seasonal pathogens, we estimated the number of deaths in elderly persons attributable to viruses and bacteria for which robust weekly laboratory surveillance data were available.

METHODS

On weekly time series (1999-2007) we used regression models to associate total death counts in individuals aged 65-74, 75-84, and ≥85 years (a population of 2.5 million) with pathogen circulation-influenza A (season-specific), influenza B, respiratory syncytial virus (RSV), parainfluenza, enterovirus, rotavirus, norovirus, Campylobacter, and Salmonella-adjusted for extreme outdoor temperatures.

RESULTS

Influenza A and RSV were significantly (P < .05) associated with mortality in all studied age groups; influenza B and parainfluenza were additionally associated in those aged ≥75 years, and norovirus was additionally associated in those aged ≥85 years. The proportions of deaths attributable to seasonal viruses were 6.8% (≥85 years), 4.4% (75-84 years), and 1.4% (65-74 years), but with great variations between years. Influenza occasionally showed lower impact than some of the other viruses.

CONCLUSIONS

The number of different pathogens associated with mortality in the older population increases with increasing age. Besides influenza A and RSV, influenza B, parainfluenza and norovirus may also contribute substantially to elderly mortality.

Attributable deaths due to influenza: a comparative study of seasonal and pandemic influenza

Influenza epidemics lead to an increase in hospitalizations and deaths. Up to now the overall impact of attributable deaths due to seasonal and pandemic influenza viruses in Austria has not been investigated in detail. Therefore we compared the number and age distribution of influenza associated deaths during ten influenza epidemic seasons to those observed during the pandemic influenza A(H1N1)2009 season. A Poisson model, relating age and daily deaths to week of influenza season using national mortality and viral surveillance data adjusted for the confounding effect of co-circulating Respiratory Syncytial Virus was used. We estimated an average of 316 influenza associated deaths per seasonal influenza epidemic (1999/2000-2008/2009) and 264 for the pandemic influenza season 2009/2010 in the area of Vienna, Austria. Comparing the mortality data for seasonal and pandemic influenza viruses in different age groups revealed a statistically significant increase in mortality for pandemic A(H1N1)2009 influenza virus in the age groups below 34 years of age and a significant decrease in mortality in those above 55 years. Our data adjusted for co-circulating RSV confirm the different mortality pattern of seasonal and pandemic influenza A(H1N1)2009 virus in different age groups.

Antibiotic therapy for pediatric community-acquired pneumonia: do we know when, what and for how long to treat?

Community-acquired pneumonia (CAP) is a common cause of morbidity among children in developed countries and accounts for an incidence of 10-40 cases per 1000 children in the first 5 years of life. Given the clinical, social and economic importance of CAP, there is general agreement that prompt and adequate therapy is essential to reduce the impact of the disease. The aim of this discussion paper is to consider critically the available data concerning the treatment of uncomplicated pediatric CAP and to consider when, how and for how long it should be treated. This review has identified the various reasons that make it difficult to establish a rational approach to the treatment of pediatric CAP, including the definition of CAP, the absence of a pediatric CAP severity score, the difficulty of identifying the etiology, limited pharmacokinetic (PK)/pharmacodynamic (PD) studies, the high resistance of the most frequent respiratory pathogens to the most widely used anti-infectious agents and the lack of information concerning the changes in CAP epidemiology following the introduction of new vaccines against respiratory pathogens. More research is clearly required in various areas, such as the etiology of CAP and the reasons for its complications, the better definition of first- and second-line antibiotic therapies (including the doses and duration of parenteral and oral antibiotic treatment), the role of antiviral treatment and on how to follow-up patients with CAP. Finally, further efforts are needed to increase vaccination coverage against respiratory pathogens and to conduct prospective studies of their impact.

Cost-effectiveness of potential infant vaccination against respiratory syncytial virus infection in The Netherlands

INTRODUCTION

Respiratory syncytial virus (RSV) infection is one of the major causes of respiratory illness in infants, infecting virtually every child before the age of 2 years. Currently, several Phase 1 trials with RSV vaccines in infants are ongoing or have been completed. As yet, no efficacy estimates are available for these vaccine candidates. Nevertheless, cost-effectiveness estimates might be informative to enable preliminary positioning of an RSV vaccine.

METHODS

A decision analysis model was developed in which a Dutch birth cohort was followed for 12 months. A number of potential vaccination strategies were reviewed such as vaccination at specific ages, a two- or three-dosing scheme and seasonal vaccination versus year-round vaccination. The impact of the assumptions made was explored in various sensitivity analyses, including probabilistic analysis. Outcome measures included the number of GP visits, hospitalizations and deaths, costs, quality-adjusted life years and incremental cost-effectiveness ratios (ICERs).

RESULTS

Currently, without vaccination, an annual number of 28,738 of RSV-related GP visits, 1623 hospitalizations, and 4.5 deaths are estimated in children in the age of 0-1 year. The total annual cost to society of RSV in the non-vaccination scenario is €7.7 million (95%CI: 1.7-16.7) and the annual disease burden is estimated at 597 QALYs (95%CI: 133-1319). In case all infants would be offered a potentially safe and effective 3-dose RSV vaccination scheme at the age of 0, 1 and 3 months, the total annual net costs were estimated to increase to €21.2 million, but 544 hospitalizations and 1.5 deaths would be averted. The ICER was estimated at €34,142 (95%CI: € 21,652-€ 87,766) per QALY gained. A reduced dose schedule, seasonal vaccination, and consideration of out-of-pocket expenses all resulted in more favorable ICER values, whereas a reduced vaccine efficacy or a delay in the timing of vaccination resulted in less favorable ICERs.

DISCUSSION

Our model used recently updated estimates on the burden of RSV disease in children and it included plausible utilities. However, due to the absence of clinical trial data, a number of crucial assumptions had to be made related to the characteristics of potential RSV vaccine. The outcomes of our modeling exercise show that vaccination of infants against RSV might be cost-effective. However, clinical trial data are warranted.

A placebo-controlled trial of Korean red ginseng extract for preventing influenza-like illness in healthy adults

Abstracts

Trial Registration

NCT01478009.

Respiratory viruses involved in influenza-like illness in a Greek pediatric population during the winter period of the years 2005-2008

Viruses are the major cause of pediatric respiratory tract infection and yet many suspected cases of illness remain uncharacterized. This study aimed to determine the distribution of several respiratory viruses in children diagnosed as having influenza‐like illness, over the winter period of 2005–2008. Molecular assays including conventional and real time PCR protocols, were employed to screen respiratory specimens, collected by clinicians of the Influenza sentinel system and of outpatient pediatric clinics, for identification of several respiratory viruses. Of 1,272 specimens tested, 814 (64%) were positive for at least one virus and included 387 influenza viruses, 160 rhinoviruses, 155 respiratory syncytial viruses, 95 adenoviruses, 81 bocaviruses, 47 parainfluenza viruses, 44 metapneumoviruses, and 30 coronaviruses. Simultaneous presence of two or three viruses was observed in 173 of the above positive cases, 21% of which included influenza virus and rhinovirus. The majority of positive cases occurred during January and February. Influenza virus predominated in children older than 1 year old, with type B being the dominant type for the first season and subtypes A/H3N2 and A/H1N1 the following two winter seasons, respectively. Respiratory syncytial virus prevailed in children younger than 2 years old, with subtypes A and B alternating from year to year. This is the most comprehensive study of the epidemiology of respiratory viruses in Greece, indicating influenza, rhinovirus and respiratory syncytial virus as major contributors to influenza‐like illness in children. J. Med. Virol. 83:1841–1848, 2011. © 2011 Wiley‐Liss, Inc.

The ins and outs of universal childhood influenza vaccination

Influenza viruses continue to cause disease of varying severity among humans. People with underlying disease and the elderly are at increased risk of developing severe disease after infection with an influenza virus. As effective and safe vaccines are available, the WHO has recommended vaccinating these groups against influenza annually. In addition to this recommendation, public health authorities of a number of countries have recently recommended vaccinating all healthy children aged 6-59 months against influenza. Here, we review the currently available data concerning the burden of disease in children, the economical impact of implementing universal vaccination of children, the efficacy of currently available influenza virus vaccines, the theoretical concerns regarding preventing immunity otherwise induced by infections with seasonal influenza viruses, and finally, how to address these concerns.

A conserved matrix epitope based DNA vaccine protects mice against influenza A virus challenge

DNA vaccination represents a unique strategy to overcome the limitations of immunization with conventional vaccines which is restricted by the high variability of influenza viruses. We evaluated the protective efficacy of a plasmid DNA (pDNA), encoding an evolutionarily conserved epitope of viral matrix protein, against the influenza A virus infection. It was found that the mice immunized via the intra-muscular route purely elicited cell mediated immune response to the pDNA, with enhanced level of Th1 cytokines viz. IL-12 and IFNγ production in the stimulated splenocyte supernatant. The cytotoxic T lymphocytes in the spleen of immunized mice significantly lysed the virus-infected MDCK cells. A significant decrease in virus replication was also observed in the lungs of immunized mice and 83% of the mice were protected against the lethal challenge of influenza A viruses. These findings suggest that the plasmid DNA expressing a single matrix epitope may serve as a promising vaccine candidate to provide effective immunity in the susceptible (mouse) population.

Absenteeism in schools during the 2009 influenza A(H1N1) pandemic: a useful tool for early detection of influenza activity in the community?

Certain influenza outbreaks, including the 2009 influenza A(H1N1) pandemic, can predominantly affect school-age children. Therefore the use of school absenteeism data has been considered as a potential tool for providing early warning of increasing influenza activity in the community. This study retrospectively evaluates the usefulness of these data by comparing them with existing syndromic surveillance systems and laboratory data. Weekly mean percentages of absenteeism in 373 state schools (children aged 4-18 years) in Birmingham, UK, from September 2006 to September 2009, were compared with established syndromic surveillance systems including a telephone health helpline, a general practitioner sentinel network and laboratory data for influenza. Correlation coefficients were used to examine the relationship between each syndromic system. In June 2009, school absenteeism generally peaked concomitantly with the existing influenza surveillance systems in England. Weekly school absenteeism surveillance would not have detected pandemic influenza A(H1N1) earlier but daily absenteeism data and the development of baselines could improve the timeliness of the system.

Excess mortality associated with influenza epidemics in Portugal, 1980 to 2004

Background

Influenza epidemics have a substantial impact on human health, by increasing the mortality from pneumonia and influenza, respiratory and circulatory diseases, and all causes. This paper provides estimates of excess mortality rates associated with influenza virus circulation for 7 causes of death and 8 age groups in Portugal during the period of 1980–2004.

Methodology/Principal Findings

We compiled monthly mortality time series data by age for all-cause mortality, cerebrovascular diseases, ischemic heart diseases, diseases of the respiratory system, chronic respiratory diseases, pneumonia and influenza. We also used a control outcome, deaths from injuries. Age- and cause-specific baseline mortality was modelled by the ARIMA approach; excess deaths attributable to influenza were calculated by subtracting expected deaths from observed deaths during influenza epidemic periods. Influenza was associated with a seasonal average of 24.7 all-cause excess deaths per 100,000 inhabitants, approximately 90% of which were among seniors over 65 yrs. Excess mortality was 3–6 fold higher during seasons dominated by the A(H3N2) subtype than seasons dominated by A(H1N1)/B. High excess mortality impact was also seen in children under the age of four years. Seasonal excess mortality rates from all the studied causes of death were highly correlated with each other (Pearson correlation range, 0.65 to 0.95, P<0.001) and with seasonal rates of influenza-like-illness (ILI) among seniors over 65 years (Pearson correlation rho>0.64, P<0.05). By contrast, there was no correlation with excess mortality from injuries.

Conclusions/Significance

Our excess mortality approach is specific to influenza virus activity and produces influenza-related mortality rates for Portugal that are similar to those published for other countries. Our results indicate that all-cause excess mortality is a robust indicator of influenza burden in Portugal, and could be used to monitor the impact of influenza epidemics in this country. Additional studies are warranted to confirm these findings in other settings.

Hospital admissions related to influenza in France during the 2006/2007 epidemic

BACKGROUND

The data available on hospital admissions related to influenza mostly concern in-patients admitted via the emergency department. Severe cases have been collated by intensive care practitioners since 2009. For this survey, we searched French hospital admission databases to estimate the prevalence rate of hospital admissions related to influenza and to record qualitative data.

METHOD

All case studies identified between October 2006 and September 2007 were split into two groups: the first displaying symptoms of clinical influenza and the second suffering from influenza as an associated diagnosis.

RESULTS

We collected 6797 hospital admissions, 2126 of which were closely related to clinical influenza. Fifty percent of cases concerned the elderly and young people. Fifty-six hospital deaths were recorded in which influenza was the underlying cause in 21% of the cases (12). When influenza was an associated diagnosis (44/56), cardiovascular or respiratory diseases were the main causes (26/44).

CONCLUSION

During the same period (2006-2007), the French Sentinel Surveillance identified only 105 hospital admissions related to influenza. Our survey was therefore more exhaustive and was able to record qualitative data. Inclusion of hospital admissions with an associated diagnosis of influenza is debatable because this decreases specificity. The relationship between the principal diagnosis and all the associated diagnoses is difficult to study, although exclusion of this type of hospitalization could significantly underestimate these figures. Despite certain limitations, French hospital admissions databases should complement French Sentinel Surveillance data.

Validation of statistical models for estimating hospitalization associated with influenza and other respiratory viruses

BACKGROUND

Reliable estimates of disease burden associated with respiratory viruses are keys to deployment of preventive strategies such as vaccination and resource allocation. Such estimates are particularly needed in tropical and subtropical regions where some methods commonly used in temperate regions are not applicable. While a number of alternative approaches to assess the influenza associated disease burden have been recently reported, none of these models have been validated with virologically confirmed data. Even fewer methods have been developed for other common respiratory viruses such as respiratory syncytial virus (RSV), parainfluenza and adenovirus.

METHODS AND FINDINGS

We had recently conducted a prospective population-based study of virologically confirmed hospitalization for acute respiratory illnesses in persons <18 years residing in Hong Kong Island. Here we used this dataset to validate two commonly used models for estimation of influenza disease burden, namely the rate difference model and Poisson regression model, and also explored the applicability of these models to estimate the disease burden of other respiratory viruses. The Poisson regression models with different link functions all yielded estimates well correlated with the virologically confirmed influenza associated hospitalization, especially in children older than two years. The disease burden estimates for RSV, parainfluenza and adenovirus were less reliable with wide confidence intervals. The rate difference model was not applicable to RSV, parainfluenza and adenovirus and grossly underestimated the true burden of influenza associated hospitalization.

CONCLUSION

The Poisson regression model generally produced satisfactory estimates in calculating the disease burden of respiratory viruses in a subtropical region such as Hong Kong.

Assessing syndromic surveillance of cardiovascular outcomes from emergency department chief complaint data in New York City

BACKGROUND

Prospective syndromic surveillance of emergency department visits has been used for near-real time tracking of communicable diseases to detect outbreaks or other unexpected disease clusters. The utility of syndromic surveillance for tracking cardiovascular events, which may be influenced by environmental factors and influenza, has not been evaluated. We developed and evaluated a method for tracking cardiovascular events using emergency department free-text chief complaints.

METHODOLOGY/PRINCIPAL FINDINGS

There were three phases to our analysis. First we applied text processing algorithms based on sensitivity, specificity, and positive predictive value to chief complaint data reported by 11 New York City emergency departments for which ICD-9 discharge diagnosis codes were available. Second, the same algorithms were applied to data reported by a larger sample of 50 New York City emergency departments for which discharge diagnosis was unavailable. From this more complete data, we evaluated the consistency of temporal variation of cardiovascular syndromic events and hospitalizations from 76 New York City hospitals. Finally, we examined associations between particulate matter ≤2.5 µm (PM(2.5)), syndromic events, and hospitalizations. Sensitivity and positive predictive value were low for syndromic events, while specificity was high. Utilizing the larger sample of emergency departments, a strong day of week pattern and weak seasonal trend were observed for syndromic events and hospitalizations. These time-series were highly correlated after removing the day-of-week, holiday, and seasonal trends. The estimated percent excess risks in the cold season (October to March) were 1.9% (95% confidence interval (CI): 0.6, 3.2), 2.1% (95% CI: 0.9, 3.3), and 1.8% (95%CI: 0.5, 3.0) per same-day 10 µg/m(3) increase in PM(2.5) for cardiac-only syndromic data, cardiovascular syndromic data, and hospitalizations, respectively.

CONCLUSIONS/SIGNIFICANCE

Near real-time emergency department chief complaint data may be useful for timely surveillance of cardiovascular morbidity related to ambient air pollution and other environmental events.

All-cause mortality during first wave of pandemic (H1N1) 2009, New South Wales, Australia, 2009

TOC Summary: Death rates from all causes were lower than in some recent influenza seasons, particularly among older persons.

In temperate countries, death rates increase in winter, but influenza epidemics often cause greater increases. The death rate time series that occurs without epidemic influenza can be called a seasonal baseline. Differentiating observed death rates from the seasonally oscillating baseline provides estimated influenza-associated death rates. During 2003–2009 in New South Wales, Australia, we used a Serfling approach with robust regression to estimate age-specific weekly baseline all-cause death rates. Total differences between weekly observed and baseline rates during May–September provided annual estimates of influenza-associated death rates. In 2009, which included our first wave of pandemic (H1N1) 2009, the all-age death rate was 6.0 (95% confidence interval 3.1–8.9) per 100,000 persons lower than baseline. In persons >80 years of age, it was 131.6 (95% confidence interval 126.2–137.1) per 100,000 lower. This estimate is consistent with a pandemic virus causing mild illness in most persons infected and sparing older persons.

Influenza vaccination and all-cause mortality in community-dwelling elderly in Ontario, Canada, a cohort study

The objective of this study was to evaluate the effectiveness of influenza vaccines in reducing all-cause mortality among community-dwelling elderly. We included 25,922 Ontario residents over age 65 who responded to population health surveys. After full adjustment, influenza vaccination was associated with a statistically significant reduction in all-cause mortality during influenza seasons (hazard ratio (HR)=0.61; 95% CI 0.47-0.79). Contrary to expectations, statistically significant associations between influenza vaccination and mortality were also observed during periods preceding (HR=0.55; 95% CI 0.40-0.75) and following (HR=0.74; 95% CI 0.59-0.94) influenza seasons, indicating the presence of residual confounding. Adjustment for functional status indicators, excluding individuals with high one-year predicted mortality at baseline, and moving the start date of follow-up failed to eliminate the refractory confounding. Since observational studies are prone to bias, future efforts to estimate vaccine effectiveness in the elderly should strive to minimize bias through improved data quality, novel data sources, and/or new analytical techniques.

Assessing the burden of paediatric influenza in Europe: the European Paediatric Influenza Analysis (EPIA) project

The European Paediatric Influenza Analysis (EPIA) project is a multi-country project that was created to collect, analyse and present data regarding the paediatric influenza burden in European countries, with the purpose of providing the necessary information to make evidence-based decisions regarding influenza immunisation recommendations for children. The initial approach taken is based on existing weekly virological and age-specific influenza-like illness (ILI) data from surveillance networks across Europe. We use a multiple regression model guided by longitudinal weekly patterns of influenza virus to attribute the weekly ILI consultation incidence pattern to each influenza (sub)type, while controlling for the effect of respiratory syncytial virus (RSV) epidemics. Modelling the ILI consultation incidence during 2002/2003-2008 revealed that influenza infections that presented for medical attention as ILI affected between 0.3% and 9.8% of children aged 0-4 and 5-14 years in England, Italy, the Netherlands and Spain in an average season. With the exception of Spain, these rates were always higher in children aged 0-4 years. Across the six seasons analysed (five seasons were analysed from the Italian data), the model attributed 47-83% of the ILI burden in primary care to influenza virus infection in the various countries, with the A(H3N2) virus playing the most important role, followed by influenza viruses B and A(H1N1). National season averages from the four countries studied indicated that between 0.4% and 18% of children consulted a physician for ILI, with the percentage depending on the country and health care system. Influenza virus infections explained the majority of paediatric ILI consultations in all countries. The next step will be to apply the EPIA modelling approach to severe outcomes indicators (i.e. hospitalisations and mortality data) to generate a complete range of mild and severe influenza burden estimates needed for decision making concerning paediatric influenza vaccination.

Global burden of acute lower respiratory infections due to respiratory syncytial virus in young children: a systematic review and meta-analysis

BACKGROUND

The global burden of disease attributable to respiratory syncytial virus (RSV) remains unknown. We aimed to estimate the global incidence of and mortality from episodes of acute lower respiratory infection (ALRI) due to RSV in children younger than 5 years in 2005.

METHODS

We estimated the incidence of RSV-associated ALRI in children younger than 5 years, stratified by age, using data from a systematic review of studies published between January, 1995, and June, 2009, and ten unpublished population-based studies. We estimated possible boundaries for RSV-associated ALRI mortality by combining case fatality ratios with incidence estimates from hospital-based reports from published and unpublished studies and identifying studies with population-based data for RSV seasonality and monthly ALRI mortality.

FINDINGS

In 2005, an estimated 33.8 (95% CI 19.3-46.2) million new episodes of RSV-associated ALRI occurred worldwide in children younger than 5 years (22% of ALRI episodes), with at least 3.4 (2.8-4.3) million episodes representing severe RSV-associated ALRI necessitating hospital admission. We estimated that 66 000-199 000 children younger than 5 years died from RSV-associated ALRI in 2005, with 99% of these deaths occurring in developing countries. Incidence and mortality can vary substantially from year to year in any one setting.

INTERPRETATION

Globally, RSV is the most common cause of childhood ALRI and a major cause of admission to hospital as a result of severe ALRI. Mortality data suggest that RSV is an important cause of death in childhood from ALRI, after pneumococcal pneumonia and Haemophilus influenzae type b. The development of novel prevention and treatment strategies should be accelerated as a priority.

FUNDING

WHO; Bill & Melinda Gates Foundation.

Survey of severe respiratory syncytial virus infection in Kyoto Prefecture from 2003 to 2007

BACKGROUND

Respiratory syncytial virus (RSV) infection in infants can develop into a severe condition.

METHODS

A survey of patients with severe RSV infection in hospitals in Kyoto Prefecture was performed from 2003 to 2007. Patients requiring intubation and those with cardiopulmonary arrest on arrival (CPAOA) were considered to have severe RSV infection.

RESULTS

Twenty-five patients with severe infection were identified and detailed data were available for 21 patients, of whom 18 required intubation and three had CPAOA. The male/female ratio was 12/9 and age ranged from 8 days to 19 years (average, 5.2 months; median: 2 months). At admission white blood cell count, lactate dehydrogenase (P < 0.05), and blood glucose (P < 0.01) were higher and Na was lower (P < 0.01) in the 18 patients with severe infection (excluding the CPAOA cases) compared to 18 sex- and age-matched patients with mild RSV infection. The incidence of bacterial infection was also higher in severe cases (P < 0.05). The outcome was death in four patients (19.0%, including two sudden deaths), aftereffects in two (9.5%), hospital discharge with improvement in 14 (66.7%), and an unclear outcome in one patient. Excluding the two sudden death cases, 14 of 19 patients (73.7%) were extubated within 2 weeks. The period of intubation was longer in older patients (P < 0.05).

CONCLUSION

Because severe RSV infection led to sudden death in two cases, detection of RSV is important at admission for an infant with CPAOA. Fourteen patients (66.7%), however, had good outcomes and most patients were extubated within 2 weeks.

Burden of influenza-related hospitalizations among children with sickle cell disease

OBJECTIVE

Children with sickle cell disease (SCD) are considered to be at high risk for complications from influenza infection despite minimal published data that characterize the burden of influenza in this population. Our objectives were to (1) estimate the rate of influenza-related hospitalizations (IRHs) among children with SCD, (2) compare this rate with rates of children with cystic fibrosis (CF) and children with neither SCD nor CF, and (3) explore mechanisms that underlie these potentially preventable hospitalizations.

METHODS

We analyzed hospitalizations from 4 states (California, Florida, Maryland, and New York) across 2 influenza seasons (2003-2004 and 2004-2005) from the Healthcare Cost and Utilization Project State Inpatient Databases. We included hospitalizations with a discharge diagnosis code for influenza in a child <18 years of age. We used census data and disease prevalence estimates to calculate denominators and compare rates of IRH among children with SCD, CF, and neither disease.

RESULTS

There were 7896 pediatric IRHs during the 2 influenza seasons. Of these, 159 (2.0%) included a co-occurring diagnosis of SCD. Annual rates of IRHs were 112 and 2.0 per 10 000 children with and without SCD, respectively, across both seasons. Children with SCD were hospitalized with influenza at 56 times (95% confidence interval: 48-65) the rate of children without SCD. Children with SCD had approximately double the risk of IRH compared with children with CF (risk ratio: 2.1 [95% confidence interval: 1.5-2.9]). IRHs among children with SCD were not longer, more costly, or more severe than IRHs among children without SCD; they were also rarely nosocomial and co-occurred with a diagnosis of asthma in 14% of cases.

CONCLUSIONS

IRHs are substantially more common among children with SCD than among those without the disease, which supports the potential importance of vigorous influenza vaccination efforts that target children with SCD.

Instrumental variables in influenza vaccination studies: mission impossible?!

OBJECTIVES

Unobserved confounding has been suggested to explain the effect of influenza vaccination on mortality reported in several observational studies. An instrumental variable (IV) is strongly related to the exposure under study, but not directly or indirectly (through other variables) with the outcome. Theoretically, analyses using IVs to control for both observed and unobserved confounding may provide unbiased estimates of influenza vaccine effects. We assessed the usefulness of IV analysis in influenza vaccination studies.

METHODS

Information on patients aged 65 years and older from the computerized Utrecht General Practitioner (GP) research database over seven influenza epidemic periods was pooled to estimate the association between influenza vaccination and all-cause mortality among community-dwelling elderly. Potential IVs included in the analysis were a history of gout, a history of orthopaedic morbidity, a history of antacid medication use, and GP-specific vaccination rates.

RESULTS

Using linear regression analyses, all possible IVs were associated with vaccination status: risk difference (RD) 7.8% (95% confidence interval [CI] 3.6%; 12.0%), RD 2.8% (95% CI 1.7%; 3.9%), RD 8.1% (95% CI 6.1%; 10.1%), and RD 100.0% (95% CI 89.0%; 111.0%) for gout, orthopaedic morbidity, antacid medication use, and GP-specific vaccination rates, respectively. Each potential IV, however, also appeared to be related to mortality through other observed confounding variables (notably age, sex, and comorbidity).

CONCLUSIONS

The potential IVs studied did not meet the necessary criteria, because they were (indirectly) associated with the outcome. These variables may, therefore, not be suited to assess unconfounded influenza vaccine effects through IV analysis.