Impact of pandemic A/H1N1/2009 influenza on children and their families: comparison with seasonal A/H1N1 and A/H3N2 influenza viruses

Caregiver Burden among Patients with Influenza or Influenza-like Illness (ILI): A Systematic Literature Review

Influenza and influenza-like illness (ILI) pose significant clinical and economic burdens globally each year. This systematic literature review examined quantitative studies evaluating the impact of patients' influenza/ILI on their caregivers' well-being, focusing on health-related quality of life (HRQoL), work productivity, and activity impairment. A comprehensive search across six databases, including the Cochrane Database of Systematic Reviews, Embase, MEDLINE via PubMed, Ovid, PsycNet, and Web of Science, yielded 18,689 records, of which 13,156 abstracts were screened, and 662 full-text articles were reviewed from January 2007 to April 2024. Thirty-six studies [HRQoL: 2; productivity: 33; both: 1] covering 22 countries were included. Caregivers of 47,758 influenza or ILI patients across 123 study cohorts were assessed in the review. The mean workday loss among caregivers ranged from 0.5 to 10.7 days per episode, influenced by patients' influenza status (positive or negative), disease severity (mild or moderate-to-severe), age, viral type (influenza A or B), and vaccination/treatment usage. The HRQoL of caregivers, including their physical and emotional well-being, was affected by a patient's influenza or ILI, where the severity and duration of a patient's illness were associated with worse HRQoL. This review shows that the consequences of influenza or ILI significantly affect not only patients but also their caregivers.

Impact of Influenza and Influenza-Like Illness on Work Productivity Outcomes: A Systematic Literature Review

BACKGROUND

Influenza is a persistent public health problem with a significant burden on patients, employers, and society. A systematic review by Keech and Beardsworth (2008) characterized the burden of influenza/influenza-like illness (ILI) on absenteeism. We conducted a systematic literature review evaluating the impact of influenza/ILI on work productivity among adults as an update to the work of Keech and Beardsworth.

METHODS

This systematic review identified studies evaluating the impact of influenza/ILI on absenteeism, presenteeism, or related work productivity measures for employees and employed caregivers based on laboratory confirmation, physician diagnosis, and/or self-reported illness. Eligible studies were in English, French, or German published from 7 March 2007 through 15 February 2022, in PubMed, Embase, or BIOSIS. Two reviewers completed screening and full-text review, with conflicts resolved by a third advisor. Summary data were extracted by two analysts; all records were quality checked by one analyst. Work productivity outcomes were summarized qualitatively, and risk of bias was not evaluated.

RESULTS

A total of 14,387 records were retrieved; 12,245 titles/abstracts were screened and 145 full-text publications were reviewed, of which 63 were included in the qualitative assessment. Studies of self-reported ILI were most frequent (49%), followed by laboratory-confirmed cases (37%) and physician diagnoses (11%). Overall, approximately 20-75% of employees missed work due to illness across study settings and populations. Mean time out of work among ill employees varied widely across study designs and populations, ranging from < 1 to > 10 days, and was often reported to be approximately 2-3 days. Considerable heterogeneity was observed across study designs, populations, and outcomes. Most employees (≈ 60-80%) reported working while experiencing influenza/ILI symptoms. Reporting of costs was sparse and heterogeneous; one study reported annual costs of influenza-related absences equating to $42,851 per 100,000 employee health plan members. Results were partitioned based on the following categories. Among otherwise healthy adults, 1-74% of workers missed ≥1 workday due to influenza/ILI, for a mean [standard deviation (SD)] of 0.5 (1.44) to 5.3 (4.50) days, and 42-89% reported working while ill, for a mean (SD) of 0.3 (0.63) to 4.4 (3.73) days. Among working caregivers, 50-75% missed work to care for children/household members with influenza/ILI, for 1-2 days on average. Similarly, the mean absenteeism among healthcare workers ranged from 0.5 to 3.2 days. Across studies evaluating vaccination status, generally smaller proportions of vaccinated employees missed time from work due to influenza/ILI.

CONCLUSIONS

This systematic review summarized the productivity burden of influenza/ILI on the worldwide working-age population. Despite notable heterogeneity in study designs, influenza/ILI case definitions, and productivity outcome measures, this review highlighted the substantial productivity burden that influenza/ILI may have on employees, employers, and society, consistent with the findings of Keech and Beardsworth (2008).

In silico method for predicting infectious strains of influenza A virus from its genome and protein sequences

Influenza A is a contagious viral disease responsible for four pandemics in the past and a major public health concern. Being zoonotic in nature, the virus can cross the species barrier and transmit from wild aquatic bird reservoirs to humans via intermediate hosts. In this study, we have developed a computational method for the prediction of human-associated and non-human-associated influenza A virus sequences. The models were trained and validated on proteins and genome sequences of influenza A virus. Firstly, we have developed prediction models for 15 types of influenza A proteins using composition-based and one-hot-encoding features. We have achieved a highest AUC of 0.98 for HA protein on a validation dataset using dipeptide composition-based features. Of note, we obtained a maximum AUC of 0.99 using one-hot-encoding features for protein-based models on a validation dataset. Secondly, we built models using whole genome sequences which achieved an AUC of 0.98 on a validation dataset. In addition, we showed that our method outperforms a similarity-based approach (i.e., blast) on the same validation dataset. Finally, we integrated our best models into a user-friendly web server 'FluSPred' (https://webs.iiitd.edu.in/raghava/fluspred/index.html) and a standalone version (https://github.com/raghavagps/FluSPred) for the prediction of human-associated/non-human-associated influenza A virus strains.

Similar severity of influenza primary and re-infections in pre-school children requiring outpatient treatment due to febrile acute respiratory illness: prospective, multicentre surveillance study (2013-2015)

Background

Influenza virus infections in immunologically naïve children (primary infection) may be more severe than in children with re-infections who are already immunologically primed. We compared frequency and severity of influenza virus primary and re-infections in pre-school children requiring outpatient treatment.

Methods

Influenza-unvaccinated children 1–5 years of age presenting at pediatric practices with febrile acute respiratory infection < 48 h after symptom onset were enrolled in a prospective, cross-sectional, multicenter surveillance study (2013–2015). Influenza types/subtypes were PCR-confirmed from oropharyngeal swabs. Influenza type/subtype-specific IgG antibodies serving as surrogate markers for immunological priming were determined using ELISA/hemagglutination inhibition assays. The acute influenza disease was defined as primary infection/re-infection by the absence/presence of influenza type-specific immunoglobulin G (IgG) and, in a second approach, by the absence/presence of subtype-specific IgG. Socio-demographic and clinical data were also recorded.

Results

Of 217 influenza infections, 178 were due to influenza A (87 [49%] primary infections, 91 [51%] re-infections) and 39 were due to influenza B (38 [97%] primary infections, one [3%] re-infection). Children with “influenza A primary infections” showed fever with respiratory symptoms for a shorter period than children with “influenza A re-infections” (median 3 vs. 4 days; age-adjusted p = 0.03); other disease characteristics were similar. If primary infections and re-infections were defined based on influenza A subtypes, 122 (87%) primary infections (78 “A(H3N2) primary infections”, 44 “A(H1N1)pdm09 primary infections”) and 18 (13%) re-infections could be classified (14 “A(H3N2) re-infections” and 4 “A(H1N1)pdm09 re-infections”). Per subtype, primary infections and re-infections were of similar disease severity. Children with re-infections defined on the subtype level usually had non-protective IgG titers against the subtype of their acute infection (16 of 18; 89%). Some patients infected by one of the influenza A subtypes showed protective IgG titers (≥ 1:40) against the other influenza A subtype (32/140; 23%).

Conclusions

Pre-school children with acute influenza A primary infections and re-infections presented with similar frequency in pediatric practices. Contrary to expectation, severity of acute “influenza A primary infections” and “influenza A re-infections” were similar. Most “influenza A re-infections” defined on the type level turned out to be primary infections when defined based on the subtype. On the subtype level, re-infections were rare and of similar disease severity as primary infections of the same subtype. Subtype level re-infections were usually associated with low IgG levels for the specific subtype of the acute infection, suggesting only short-time humoral immunity induced by previous infection by this subtype. Overall, the results indicated recurring influenza virus infections in this age group and no or only limited heterosubtypic antibody-mediated cross-protection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06988-7.

Epidemic and pandemic viral infections: impact on tuberculosis and the lung: A consensus by the World Association for Infectious Diseases and Immunological Disorders (WAidid), Global Tuberculosis Network (GTN), and members of the European Society of Clinical Microbiology and Infectious Diseases Study Group for Mycobacterial Infections (ESGMYC)

Major epidemics, including some that qualify as pandemics, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), HIV, influenza A (H1N1)pdm/09 and most recently COVID-19, affect the lung. Tuberculosis (TB) remains the top infectious disease killer, but apart from syndemic TB/HIV little is known regarding the interaction of viral epidemics and pandemics with TB. The aim of this consensus-based document is to describe the effects of viral infections resulting in epidemics and pandemics that affect the lung (MERS, SARS, HIV, influenza A (H1N1)pdm/09 and COVID-19) and their interactions with TB. A search of the scientific literature was performed. A writing committee of international experts including the European Centre for Disease Prevention and Control Public Health Emergency (ECDC PHE) team, the World Association for Infectious Diseases and Immunological Disorders (WAidid), the Global Tuberculosis Network (GTN), and members of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) Study Group for Mycobacterial Infections (ESGMYC) was established. Consensus was achieved after multiple rounds of revisions between the writing committee and a larger expert group. A Delphi process involving the core group of authors (excluding the ECDC PHE team) identified the areas requiring review/consensus, followed by a second round to refine the definitive consensus elements. The epidemiology and immunology of these viral infections and their interactions with TB are discussed with implications for diagnosis, treatment and prevention of airborne infections (infection control, viral containment and workplace safety). This consensus document represents a rapid and comprehensive summary on what is known on the topic.

Reduced Prescription of Baloxavir After Suspected Prevalence of a Baloxavir-Resistant Influenza Virus Strain and the Emergence of SARS-CoV-2 in a Tertiary Hospital in Japan

Objective

The use of baloxavir, a new anti-influenza agent, began in Japan from the 2018 to 2019 season and became the focus of attention due to its efficient viral reduction ability; therefore, we should know the prescription changes of anti-influenza agents.

Methods

We analyzed the changes in the prescription of anti-influenza agents between the 2018-19 season and the 2019-20 season in our hospital.

Results

The share of baloxavir was 15%, while the shares of oseltamivir and laninamivir were 42% and 31%, respectively in the 2018-2019 season. However, in the 2019-20 season, the share of baloxavir and laninamivir was reduced to 3% and 17%, respectively, in contrast to an increase in the share of oseltamivir (66%). The total prescription of anti-influenza agents for patients decreased in the 2019-20 season (205 patients), compared with the 2018-19 season (509 patients).

Conclusion

These results suggest significant changes such as a reduction in the prescription of anti-influenza agents, especially baloxavir, likely due to the suspected prevalence of a baloxavir-resistant strain of influenza virus and the emergence of SARS-CoV-2 in Japan.

Adult influenza A (H3N2) with reduced susceptibility to baloxavir or peramivir cured after switching anti-influenza agents

We describe two adults with A/H3N2 influenza with (patient 1), and without (patient 2) polymerase acidic (PA) subunit I38 T substitution during the same season. Patient 1 had a reduced clinical response to baloxavir, a cap-dependent endonuclease inhibitor (CEI), but was cured by peramivir, a neuraminidase inhibitor. Baloxavir was clinically effective for patient 2, for whom peramivir had been ineffective. Susceptibility to baloxavir can be decreased by a PA unit mutation, but response to treatment can be increased by switching and/or combination with a neuraminidase inhibitor, even though CEI are clinically effective against influenza in adults.

Characteristics of hospitalised patients with influenza in 2015-2016 in northern Israel: three circulating strains and continued fear of 2009 A/H1N1

This study aimed to characterise children and adults diagnosed with influenza who were admitted to three medical centres in northern Israel in the winter of 2015-2016, a unique season due to infection with three types of influenza strains: A/H1N1, A/non-H1N1 and B. Data were collected retrospectively from medical records. Influenza A/H1N1 infected mainly adults (61% vs. 16% in children, P < 0.001) while influenza B was the common type in children (54% vs. 28% in adults, P < 0.001). Adults (36% vs. 5% in children, P < 0.001) and patients infected with A/H1N1 had higher rates of pneumonia (34% vs. 16% and 14% in influenza B and A/non-H1N1, respectively, P = 0.002). Treatment with oseltamivir was prescribed to 90% of patients; adults had higher rates of treatment (96% vs. 84% in children, P = 0.002) as well as patients infected with A/H1N1 (96% vs. 86% in influenza B and A/non-H1N1, respectively, P = 0.04). Oseltamivir was given after a mean of 3.6 days of symptoms. Preferential infection of adults by A/H1N1 was evident in Israel in 2015-2016; pneumonia rates were higher in adults and in A/H1N1-infected patients. Oseltamivir was prescribed to most patients but especially to those infected with A/H1N1, and was given relatively late in the course of the disease.

Subtype-specific Clinical Presentation, Medical Treatment and Family Impact of Influenza in Children 1-5 Years of Age Treated in Outpatient Practices in Germany During Three Postpandemic Years, 2013-2015

BACKGROUND

Limited data on the influenza burden in pediatric outpatients are available, especially regarding direct comparison of the cocirculating (sub)types A(H1N1)pdm09, A(H3N2) and B.

METHODS

Children 1-5 years of age, unvaccinated against influenza and presenting with febrile acute respiratory infections (ARIs), were enrolled in 33 pediatric practices in Germany from 2013 to 2015 (January-May). Influenza was confirmed by multiplex polymerase chain reaction from pharyngeal swabs and (sub)typed.

RESULTS

In 805 children with ARI, influenza was the most frequently detected respiratory virus (n = 305; 37.9%). Of 217 influenza patients included, 122 (56.2%) were infected with A(H3N2), 56 (25.8%) with A(H1N1)pdm09 and 39 (18.0%) with B. Median age was 3.7 years [interquartile range (IQR), 2.1-4.8]; 11% had underlying conditions. Median fever duration was 4 days (IQR, 3-5), and the disease duration was 9 days (IQR, 7-12). Most frequent diagnoses were pharyngitis (26%), bronchitis (18%) and acute otitis media (10%). Children received mainly antipyretics (86%) and adrenergic nasal drops/spray (53%); 9% received antibiotics and 3% oseltamivir. Thirty-six percent required at least 1 additional practice visit; 1% was hospitalized. Median absences from childcare were 5 days (IQR, 3-7); parents lost 4 workdays (IQR, 2-6). Symptoms, severity and impact on the family were largely unrelated to (sub)type. However, patients with A(H1N1)pdm09 had fewer underlying conditions (P = 0.017), whereas patients with B more often had pharyngitis (P = 0.022), acute otitis media (P = 0.012) and stenosing laryngotracheitis (P = 0.007).

CONCLUSIONS

Influenza was the most frequently detected viral pathogen in outpatient children with febrile, mostly uncomplicated ARI. In this setting, clinical manifestations and severity were similar across the (sub)types prevalent during the postpandemic seasons.

Clinical characteristics and severity of influenza infections by virus type, subtype, and lineage: A systematic literature review

Aim

Studies carried out in the early 2000s found that the number of influenza‐associated hospitalizations and deaths was highest in seasons dominated by A(H3N2), suggesting that the clinical presentation and severity of influenza may differ across virus types, subtypes, and lineages. We aimed to review the studies that examined this hypothesis.

Method

We conducted a literature review of studies published until January 2017 that compared the clinical presentation, disease severity, and case‐fatality ratio of influenza patients infected with different virus types (A, B), subtypes (pre‐pandemic A(H1N1), A(H1N1)p, A(H3N2)), and lineages (Victoria, Yamagata).

Results

The literature search resulted in over 1700 entries: After applying in‐ and exclusion criteria, 47 studies were included in the literature review. Studies showed a wide diversity in setting and populations. Only a minority of studies provided results adjusted by patient's age and other potential confounders. There were very few differences in the clinical presentation of patients infected with different influenza viruses. We found weak evidence that the A(H1N1)p subtype in the post‐pandemic period was more often associated with secondary bacterial pneumonia, ICU admission, and death, than the other influenza virus (sub)types.

Conclusion

Contrary to what is commonly assumed, the causal virus subtype does not seem to be a major determinant of clinical presentation and severity of influenza illness. However, drawing conclusions was made difficult by the low comparability and methodological shortcomings of included studies, and more well‐designed studies are warranted.

Eliciting unnatural immune responses by activating cryptic epitopes in viral antigens

Antigenic variation in viral surface antigens is a strategy for escaping the host's adaptive immunity, whereas regions with pivotal functions for infection are less subject to antigenic variability. We hypothesized that genetically invariable and immunologically dormant regions of a viral surface antigen could be exposed to the host immune system and activated by rendering them susceptible to antigen-processing machinery in professional antigen-presenting cells (APCs). Considering the frequent antigen drift and shift in influenza viruses, we identified and used structural modeling to evaluate the conserved regions on the influenza hemagglutinin (HA) surface as potential epitopes. Mutant viruses containing the cleavage motifs of cathepsin S within HA were generated. Immunization of mice showed that the mutant, but not the wild-type virus, elicited specific antibodies against the cryptic epitope. Those antibodies were purified, and specific binding to HA was confirmed. These results suggest that an unnatural immune response can be elicited through the processing of target antigens in APCs, followed by presentation via the major histocompatibility complex, if not subjected to regulatory pathways. By harnessing the antigen-processing machinery, our study shows a proof-of-principle for designer vaccines with increased efficacy and safety by either activating cryptic, or inactivating naturally occurring, epitopes of viral antigens.-Lee, Y. J., Yu, J. E., Kim, P., Lee, J.-Y., Cheong, Y. C., Lee, Y. J., Chang, J., Seong, B. L. Eliciting unnatural immune responses by activating cryptic epitopes in viral antigens.

Prevalence, genetic drift of haemagglutinin, and antiviral resistance of influenza A/H3N2 viruses circulating in Shanghai in children during 2009-2012

Influenza A/H3N2 viruses are associated with severe epidemics. Antiviral resistance and continued antigenic drift are the major concerns regarding prophylaxis and treatment of influenza. The objectives of this study were to investigate the prevalence and frequency of antiviral drug resistance in influenza A/H3N2 viruses circulating among Shanghainese children from June 2009 to May 2012 and to understand the genetic evolution of the hemagglutinin (HA) epitopes. Nasopharyngeal/throat swabs were collected from outpatients with influenza-like illness. Of the 3,475 children tested, 344 (9.9%) were positive for influenza A/H3N2 viruses. Epidemics of influenza A/H3N2 occurred in July-September 2009, August 2010-January 2011, and November 2011-May 2012. The 71 A/H3N2-positive specimens were sequenced to characterize the genotypic antiviral resistance and genetic drift in the HA epitopes. All of the 71 A/H3N2 viruses sequenced were genotypically resistant to adamantine but sensitive to oseltamivir. The HA1 sequence analysis revealed that the A/H3N2 viruses underwent constant mutations in the HA antigenic sites over the three seasons compared with the corresponding vaccine strains, and amino acid changes in at least three epitopes were observed each season. Phylogenic analyses indicated that the A/H3N2 strains circulating in Shanghai fell into clades different from those of the corresponding seasonal vaccine strains and were grouped into the A/Perth/16/2009 genetic clade and the A/Victoria/208/2009 genetic clades 3B, 3C, and 5. The continuous monitoring of genetic drift and antiviral resistance of influenza viruses is important for the management of influenza and for updating the vaccine composition.

Influenza pneumonia among adolescents and adults: a concurrent comparison between influenza A (H1N1) pdm09 and A (H3N2) in the post-pandemic period

Introduction

Comparisons of the characteristics between the influenza A (H1N1) pdm09 and common seasonal influenza are important for both clinical management and epidemiological studies. However, the differences between pandemic and seasonal influenza during the post-pandemic period are poorly understood.

Objectives

The aim of our research was to investigate clinical and immune response differences between patients with influenza A (H1N1) pdm09 pneumonia and seasonal influenza A (H3N2) pneumonia in the post-pandemic period.

Methods

During the first flu season in post-pandemic period, patients from Beijing Network for Adult Community-Acquired Pneumonia present A (H1N1) pdm09 or A (H3N2) influenza were compared concurrently in the aspects of clinical characteristics and inflammatory profile in acute phase.

Result

Patients with A (H1N1) pdm09 influenza pneumonia showed a close mean age to A (H3N2) pneumonia (51 ± 20 vs 53 ± 16, mean ± standard deviation, years) but tended to have more underlying diseases (32.8% vs 10%, P = 0.036). Although clinical characteristics were similar, no statistical difference were found in pneumonia severity index (PSI) score or intensive care unit admission rate or mortality, patients in A (H1N1) pdm09 cohort present higher levels of aspartate aminotransferase, lactase dehydrogenase (P = 0.006, 0.018, respectively) in blood and also longer duration of fever than A (H3N2) cohort. Levels of interleukin (IL)-10 and IL-12 (p70) were higher in A (H1N1) pdm09 cohort (P = 0.031, 0.047, respectively).

Conclusios

During the first post-pandemic flu season, patients with the A (H1N1) pdm09 pneumonia showed similar clinical characteristics but slightly higher disease severity and stronger systemic inflammatory response than A (H3N2) pneumonia.

Comparative analysis of clinical characteristics of pandemic influenza a/h1n1 and seasonal influenza a infections in hospitalized children

Pandemic influenza A/H1N1 (piA) caused significant morbidity and mortality worldwide. We compared characteristics of piA (2009/2010) to those of seasonal influenza A (2007/2008/2009) in 134 (piA/seasonal influenza A: N = 55/79) hospitalized patients <18 years of age. Chronic disease was present in 25%/33%. Most common symptoms were fever (87%/94%), cough (78%/86%), rhinitis (76%/76%) and pharyngitis (67%/68%). Croup syndrome (15%/3%), conjunctivitis (31%/10%) and febrile seizures (26%/13%) were more frequent in piA; 64%/53% patients had ≥1 complication, and 5 (3/2) were admitted to intensive care unit. Oseltamivir use was 20%/0%. Severity of pandemic influenza disease was not different compared with seasonal influenza A in preceding years.

Childhood influenza in the outpatient setting in Shanghai, China

BACKGROUND

Influenza is a common cause of outpatient visits in childhood. Influenza vaccine has been widely used for children ≥ 6 months of age in developed countries based on accumulating evidence on the substantial socioeconomic burden of influenza in children. However, the data of childhood influenza in China are scarce.

METHODS

We carried out a prospective surveillance of influenza among children visiting outpatient clinic for influenza-like illness between June 2009 and May 2011. Respiratory samples were obtained from the enrolled cases and the demographic and clinical data were collected.

RESULTS

Of 2356 enrolled cases, influenza was virologically confirmed in 608 (25.81%) otherwise healthy children. Four hundred sixty-eight (76.97%) were influenza A positive (A/H3N2:236, pandemic A/H1N1:219, seasonal A/H1N1:4, A/H3N2 coinfected with pandemic A/H1N1:3, untyped:6) and 142 (23.35%) were influenza B positive (2 coinfected with pandemic A/H1N1). The outbreaks of A/H3N2, pandemic A/H1N1 and influenza B took place in fall, winter and spring, alternatively. More institutionalized children were affected when the outbreaks overlapped with school opening. Among 603 children with a single influenza virus infection, 289 (47.93%) were <3 years old and 283 (46.93%) had close contact with persons who had fever or respiratory infection, of whom, 192 (67.84%) contacts were family members.

CONCLUSION

The annual outbreak of influenza led to a high rate of outpatient visits among children in Shanghai. Outbreaks occurred in younger and institutionalized children. Household members were the main disseminators to spread influenza among children.

Two years after pandemic influenza A/2009/H1N1: what have we learned?

The world had been anticipating another influenza pandemic since the last one in 1968. The pandemic influenza A H1N1 2009 virus (A/2009/H1N1) finally arrived, causing the first pandemic influenza of the new millennium, which has affected over 214 countries and caused over 18,449 deaths. Because of the persistent threat from the A/H5N1 virus since 1997 and the outbreak of the severe acute respiratory syndrome (SARS) coronavirus in 2003, medical and scientific communities have been more prepared in mindset and infrastructure. This preparedness has allowed for rapid and effective research on the epidemiological, clinical, pathological, immunological, virological, and other basic scientific aspects of the disease, with impacts on its control. A PubMed search using the keywords "pandemic influenza virus H1N1 2009" yielded over 2,500 publications, which markedly exceeded the number published on previous pandemics. Only representative works with relevance to clinical microbiology and infectious diseases are reviewed in this article. A significant increase in the understanding of this virus and the disease within such a short amount of time has allowed for the timely development of diagnostic tests, treatments, and preventive measures. These findings could prove useful for future randomized controlled clinical trials and the epidemiological control of future pandemics.

Clinical and socioeconomic impact of pediatric seasonal and pandemic influenza

Influenza is frequent among otherwise healthy day-care and school-aged children. Recent studies have demonstrated its significant effect on various outcome factors, including significantly more school and parental work absenteeism, and secondary illnesses among family members. Other studies have shown that the potential benefit of vaccinating children against influenza extends to other members of their families, thus supporting earlier economic modeling analyses of immunization programs. Although there are some differences in the clinical and socio-economic impact of seasonal and pandemic influenza, the benefits of vaccination are similar in both cases. The vaccination of otherwise healthy children may significantly reduce direct and indirect influenza-related costs, which supports the recommendation to make wider use of influenza vaccine in healthy children of any age in order to reduce the burden of infection on the community.