Influenza Infection In Children Research Articles

Predictors of complicated influenza infection in children presenting in a tertiary hospital in a tropical country: A case-control study

Influenza causes significant healthcare burden globally1 with highest risks in children and the elderly. In children, multiple studies have identified risk factors for severe influenza such as young age (<5 years), presence of comorbidities, abnormal vital signs (e.g. hypoxia, shock) and bacterial coinfections.2-4 We found similar findings in our centre which included children during the influenza A (H1N1) 2009 pandemic with age <2 years and comorbidity as risk factors for complicated influenza.5

MUC5AC: A potential biomarker of severity in pediatric patients infected with influenza.

Numerous factors can increase the risk of severe influenza; however, a majority of severe cases occur in previously healthy children. Identification of high-risk children is important for targeted preventive interventions and prompt treatment. The aim of this study was to evaluate MUC5AC as a biomarker for influenza disease severity in children. For this, aprospective cohort study was conducted in 2019. Children hospitalized with acute respiratory infection (ARI) with confirmed positive influenza infection were enrolled. Influenza cases were identified by reverse transcriptase-polymerase chain reaction. Life-threatening disease (LTD) was defined by the need for intensive care and ventilatory support. MUC5AC, epidemiologic, and clinical risk factors were assessed. Three hundred and forty-two patients were hospitalized with ARI, of which 49 (14%) had confirmed influenza infection and 6 (12%) of them developed LTD. MUC5AC levels were higher in those patients with mild diseasecompared to cases with poorer outcomes. Our results show that the severity of influenza infection in children is significantly associated with low levels of MUC5AC. These findings suggest its potential as a suitable biomarker for predicting disease severity.

Respiratory Syncytial Virus and Influenza Infections in Children in Ulaanbaatar, Mongolia, 2015-2021.

Data available for RSV and influenza infections among children < 2 years in Mongolia are limited. We present data from four districts of Ulaanbaatar from April 2015 to June 2021. This study was nested in an enhanced surveillance project evaluating pneumococcal conjugate vaccine (PCV13) impact on the incidence of hospitalized lower respiratory tract infections (LRTIs). Our study was restricted to children aged < 2 years with arterial O2 saturation < 93% and children with radiological pneumonia. Nasopharyngeal (NP) swabs collected at admission were tested for RSV and influenza using qRT-PCR. NP swabs of all patients with radiological pneumonia and of a subset of randomly selected NP swabs were tested for S. pneumoniae (S.p.) by qPCR and for serotypes by culture and DNA microarray. Among 5705 patients, 2113 (37.0%) and 386 (6.8%) had RSV and influenza infections, respectively. Children aged 2-6 months had a higher percentage of very severe RSV infection compared to those older than 6 months (42.2% versus 31.4%, p-value Fisher's exact = 0.001). S.p. carriage was detected in 1073/2281 (47.0%) patients. Among S.p. carriage cases, 363/1073 (33.8%) had S.p. and RSV codetection, and 82/1073 (7.6%) had S.p. and influenza codetection. S.p. codetection with RSV/influenza was not associated with more severe LRTIs, compared to only RSV/influenza cases. In Mongolia, RSV is an important pathogen causing more severe LRTI in children under 6 months of age. Codetection of RSV or influenza virus and S.p. was not associated with increased severity.

The Clinical Predictors of and Vaccine Protection Against Severe Influenza Infection in Children.

Influenza infection in children causes a tremendous global burden. In this study, we aimed to investigate the clinical predictors of severe influenza among children. We retrospectively included hospitalized children who had laboratory-confirmed influenza infection and were admitted to a medical center in Taiwan between 2010 and 2018. Severe influenza infection was defined as needing intensive care. We compared demographics, comorbidities, vaccine status and outcomes between patients with severe and nonsevere infection. There were 1,030 children hospitalized for influenza infection: 162 patients needed intensive care and 868 patients did not. Multivariable analysis revealed that an age below 2 years (adjusted odds ratio [aOR] 3.31, 95% CI 2.22-4.95), underlying cardiovascular disease (aOR 1.84, 95% CI 1.04-3.25), neuropsychological (aOR 4.09, 95% CI 2.59-6.45) or respiratory disease (aOR 3.87, 95% CI 1.42-10.60), patchy infiltrates (aOR 2.52, 95% CI 1.29-4.93), pleural effusion (aOR 6.56, 95% CI 1.66-25.91) and invasive bacterial coinfection (aOR 21.89, 95% CI 2.19-218.77) were significant clinical predictors of severe disease, whereas severe infection was less likely in individuals who had received influenza and pneumococcal conjugate vaccines (PCVs) (aOR 0.51, 95% CI 0.28-0.91; aOR 0.35, 95% CI 0.23-0.51, respectively). The most significant risk factors associated with severe influenza infection were an age under 2 years, comorbidities (cardiovascular, neuropsychological, and respiratory diseases), patchy infiltrates or effusion shown on chest X-rays, and bacterial coinfections. The incidence rate of severe disease was significantly lower in those who had received influenza vaccines and PCVs. This article is protected by copyright. All rights reserved.

Obesity as a risk factor for severe influenza infection in children and adolescents: a systematic review and meta-analysis.

The findings of our meta-analysis suggest that obesity in children with influenza is associated with a worse prognosis, both hospitalization and ICU admission/death. • Obesity has been identified as a risk factor for non-communicable as well as communicable diseases. • A previous meta-analysis failed to demonstrate a statistically significant association between obesity and influenza infection severity. • Children with high BMI and influenza infection are more likely to get hospitalized. • Pediatric inpatients with increased BMI and influenza infection may have a worse prognosis.

DDX58 Is Associated With Susceptibility to Severe Influenza Virus Infection in Children and Adolescents.

Seasonal influenza virus infection causes a range of disease severity, including lower respiratory tract infection with respiratory failure. We evaluated the association of common variants in interferon (IFN) regulatory genes with susceptibility to critical influenza infection in children. We performed targeted sequencing of 69 influenza-associated candidate genes in 348 children from 24 US centers admitted to the intensive care unit with influenza infection and lacking risk factors for severe influenza infection (PICFlu cohort, 59.4% male). As controls, whole genome sequencing from 675 children with asthma (CAMP cohort, 62.5% male) was compared. We assessed functional relevance using PICFlu whole blood gene expression levels for the gene and calculated IFN gene signature score. Common variants in DDX58, encoding the retinoic acid-inducible gene I (RIG-I) receptor, demonstrated association above or around the Bonferroni-corrected threshold (synonymous variant rs3205166; intronic variant rs4487862). The intronic single-nucleotide polymorphism rs4487862 minor allele was associated with decreased DDX58 expression and IFN signature (P < .05 and P = .0009, respectively) which provided evidence supporting the genetic variants' impact on RIG-I and IFN immunity. We provide evidence associating common gene variants in DDX58 with susceptibility to severe influenza infection in children. RIG-I may be essential for preventing life-threatening influenza-associated disease.

Vital sign predictors of severe influenza among children in an emergent care setting.

BackgroundDecisions regarding the evaluation of children with influenza infection rely on the likelihood of severe disease. The role of early vital signs as predictors of severe influenza infection in children is not well known. Our objectives were to determine the value of vital signs in predicting hospitalization/recurrent emergency department (ED) visits due to influenza infection in children.MethodsWe conducted a prospective study of children aged 6 months to 8 years of age with influenza like illness evaluated at an ED/UC from 2016–2018. All children underwent influenza testing by PCR. We collected heart rate, respiratory rate and temperature, and converted heart rate (HR) and respiratory rate (RR) to z-scores by age. HR z scores were further adjusted for temperature. Our primary outcome was hospitalization/recurrent ED visits within 72 hours. Vital sign predictors with p< 0.2 and other clinical covariates were entered into a multivariable logistic regression model to determine odds ratios (OR) and 95% CI; model performance was assessed using the Brier score and discriminative ability with the C statistic.ResultsAmong 1478 children, 411 (27.8%) were positive for influenza, of which 42 (10.2%) were hospitalized or had a recurrent ED visit. In multivariable analyses, adjusting for age, high-risk medical condition and school/daycare attendance, higher adjusted respiratory rate (OR 2.09, 95%CI 1.21–3.61, p = 0.0085) was a significant predictor of influenza hospitalization/recurrent ED visits.ConclusionsHigher respiratory rate adjusted for age was the most useful vital sign predictor of severity among young children with PCR-confirmed influenza.

A trend for decrease of influenza infections in children during the first wave of COVID-19 observed in a Chinese hospital

Article A trend for decrease of influenza infections in children during the first wave of COVID-19 observed in a Chinese hospital was published on October 1, 2021 in the journal Journal of Laboratory Medicine (volume 45, issue 4-5).

Association between Dental Caries and Influenza Infection in Children: A Japanese Nationwide Population-Based Study.

Dental caries is the most common chronic childhood disease. Recent studies have suggested that dental caries harbor respiratory infections in adults. We investigated the association between dental caries and influenza in children. In this study, 42,812 children aged 2.5 years, 38,540 children aged 5.5 years, and 34,124 children aged 10 years were included in the analysis from the Longitudinal Survey of Newborns in the 21st Century in Japan, which targeted all children born during a certain period in 2001. We used information on dental caries treated at hospitals and clinics in the past year as exposure and influenza as outcome during the observation periods (1.5–2.5, 4.5–5.5, and 9–10 years of age). We performed a log-binomial regression analysis, adjusting for potential confounders, and stratified analysis according to previous dental caries status. The presence of dental caries increased the incidence of influenza in all three target ages compared with the absence of dental caries. The incidence of influenza increased with the presence of current dental caries, regardless of the presence of past dental caries. These associations were observed irrespective of household income. Early detection and treatment of dental caries may reduce the risk of influenza in children.

Routine blood parameters are helpful for early identification of influenza infection in children

BackgroundRoutine blood parameters, such as the lymphocyte (LYM) count, platelet (PLT) count, lymphocyte-to-monocyte ratio (LMR), neutrophil-to-lymphocyte ratio (NLR), lymphocytes multiplied by platelets (LYM*PLT) and mean platelet volume-to-platelet ratio (MPV/PLT), are widely used to predict the prognosis of infectious diseases. We aimed to explore the value of these parameters in the early identification of influenza virus infection in children.MethodsWe conducted a single-center, retrospective, observational study of fever with influenza-like symptoms in pediatric outpatients from different age groups and evaluated the predictive value of various routine blood parameters measured within 48 h of the onset of fever for influenza virus infection.ResultsThe LYM count, PLT count, LMR and LYM*PLT were lower, and the NLR and MPV/PLT were higher in children with an influenza infection (PCR-confirmed and symptomatic). The LYM count, LMR and LYM*PLT in the influenza infection group were lower in the 1- to 6-year-old subgroup, and the LMR and LYM*PLT in the influenza infection group were lower in the > 6-year-old subgroup. In the 1- to 6-year-old subgroup, the cutoff value of the LMR for predicting influenza A virus infection was 3.75, the sensitivity was 81.87%, the specificity was 84.31%, and the area under the curve (AUC) was 0.886; the cutoff value of the LMR for predicting influenza B virus infection was 3.71, the sensitivity was 73.58%, the specificity was 84.31%, and the AUC was 0.843. In the > 6-year-old subgroup, the cutoff value of the LMR for predicting influenza A virus infection was 3.05, the sensitivity was 89.27%, the specificity was 89.61%, and the AUC was 0.949; the cutoff value of the LMR for predicting influenza B virus infection was 2.88, the sensitivity was 83.19%, the specificity was 92.21%, and the AUC was 0.924.ConclusionsRoutine blood tests are simple, inexpensive and easy to perform, and they are useful for the early identification of influenza virus infection in children. The LMR had the strongest predictive value for influenza virus infection in children older than 1 year, particularly in children older than 6 years with influenza A virus infection.

Diagnostic difficulties of AH1N1 influenza infection in children with acute lymphoblastic leukemia

Introduction:Children with acute lymphoblastic leukemia (ALL) are at a risk of developing influenza-related complications. Approximately 10% of influenza-infected children with ALL or other types of cancer need intensive care, and 5% of them eventually die.Patients’ concerns:We report 2 children with ALL and the swine-origin influenza A virus infection. Diagnosing influenza in them was a challenge. Medical records of these children were reviewed for demographic, clinical, and laboratory data. Patients were hospitalized in the Department of Pediatric Hematology, Oncology, and Transplantology of the Medical University of Lublin, Poland. Case 1 involved a 2-year-old girl who, according to acute lymphoblastic leukemia intercontinental Berlin-Frankfürt-Münster protocol 2009, started chemotherapy in July 2015. She was categorized in the intermediate risk group and received the induction and consolidation phase of the therapy without severe complications. The reinduction therapy was administered in the outpatient department till the 15th day. On the 20th day of this phase, she was admitted to our department with fever, mucositis, tachypnea, abdominal pain, and diarrhea. In September 2009, a 14-year-old boy (case 2) who, according to acute lymphoblastic leukemia intercontinental Berlin-Frankfürt-Münster protocol 2002, was categorized in the high-risk (HR) group, received the induction (Protocol I) phase of therapy without severe complications. On the 7th day of the HR-1 course, he manifested fever and strong, tiring cough, followed by strong mucositis. Chemotherapy had to be interrupted in both children.Diagnosis:Respiratory viral infections, causing pneumonia, occurred in both patients during anticancer treatment. Initially, the real-time polymerase chain reaction test for the swine-origin influenza A was negative in both patients, which delayed the diagnosis. Additionally, bacterial, and fungal complications were also observed.Interventions:Both patients received oseltamivir twice a day, a broad-spectrum antibiotic, antifungal drug, and granulocyte colony growth factor.Outcomes:The disease progressed quickly, and our patients subsequently died.Conclusion:We speculated that early antiviral treatment can help in the better management of patients in the HR group. It is also important to minimize influenza morbidity and mortality by vaccinating family members, using empiric therapy, providing immediate antiviral therapy, and educating parents about hygiene measures.

Nontraditional Uses of Live Attenuated Influenza Vaccine: School-Located Influenza Vaccination.

Immunization against influenza continues to be the best method of preventing influenza infection in children, and additionally, indirectly helping to lower disease in adults, given the role of children as "spreaders" of influenza to the community at large. An increasing evidence base exists for the use of school-located influenza vaccination (SLIV) programs to increase the influenza vaccination rates among children. Live, attenuated influenza vaccine (LAIV) has unique characteristics that make it useful for SLIV programs, including ease of immunization without needles, faster delivery, and in many (but not all) years, good vaccine effectiveness. Reviewed herein are results of selected published trials as well as guidance on planning a successful SLIV program.

Brain Complications with Influenza Infection in Children

Objectives: To summarize the characteristics and research progress of influenza-associated brain complications in children and provide references for early diagnosis and brain protection treatment. Methods: Studied published articles of influenza-associated neurocomplications in children from PubMed and summarizes them from epidemiology, clinical manifestations, diagnosis and treatment, and basic research progress. Results: Common brain complications in flu-children include febrile seizures, influenza-associated encephalopathy (IAE), acute or post-influenza encephalitis, and the most severe condition is acute necrotizing encephalopathy (ANE). However, the mechanism and relevant factors of influenza-associated brain damage have not been elucidated. Conclusion: Influenza could be accompanied by various brain lesion complications in dif ferent stages of the disease, some of which are life-threatening or leave severe neurological sequelae, such as ANE. Due to different brain injury mechanisms, specific early diagnosis and brain protection treatment for different complications are unclear or unanimous. Therefore, further classification and basic research are needed.

PIN27 ECONOMIC AND QUALITY OF LIFE BURDEN OF PAEDIATRIC INFLUENZA IN AUSTRALIA

Children have a disproportionately higher risk of influenza-related morbidity and mortality. Despite this, immunisation against influenza is not universally funded for children in Australia. The aim of this study was to evaluate the quality of life burden and healthcare resource utilisation attributable to influenza in children within the Australian setting from published sources. Literature searches of the Medline database using the PubMed platform were performed in November 2018. Data on influenza-related resource utilisation were extracted from seven studies and six studies evaluating quality of life burden of influenza were investigated. The majority of resource use studies were prospective cohort studies reporting both the direct and indirect burden of influenza in children in hospital (n=2) or community-based settings (n=4). The mean cost per episode of community-managed disease was estimated in three studies as $240.88 [2001/2002 costs], $308.70 [2003 costs] and $626 [2010 costs]. The key cost driver was carer time away from usual activities and work, making up 78% of total costs (range 64.8-91.2%), followed by healthcare visits. Resource utilisation estimates without cost-related information were reported in another three studies, whilst one cost-of-illness study estimated that the cost of influenza-related illness in a typical season is $115 million from the perspective of the Australian healthcare system. A quality of life study relevant to the Australian setting derived a utility weight for a day with influenza symptoms of 0.5579. The quality of life implications and economic burden of influenza infection in children are significant, particularly when indirect societal costs such as carer absenteeism and lost productivity are considered. This summary of the available data will help inform the cost-effectiveness of a universal influenza vaccine program in children.

Spectrum of H1N1 influenza infection in Indian children: A tertiary centre experience

Objective: To study the clinical profile, severity, outcome and risk factors for H1N1 influenza infection in children <18 years. Method: Children <18 years admitted to the Paediatric Department of our hospital and confirmed to have H1N1pdm2009 influenza infection from December 2016 to November 2017 were included. We reviewed the case sheets of the study population and captured the required data. Illness was classified as mild, progressive or severe illness and treated as per CDC guidelines. Outcome measures analysed included – mortality, duration of ICU / hospital stay, need for oxygen supplementation or assistive ventilation. Results: Our study involved analysis of 31 children. We found clustering of cases from 1-5 years accounting for 56% with no sex predilection. We observed a bimodal seasonal peak in incidence of infection from December to February (32%) and June to August (42%). Malnutrition was most common risk factor affecting 15/31 (48.4%) children followed by pre-existing medical illness 10/31 (30%). Risk stratification done as per CDC recommended guidelines showed the majority of the children (64.5%) manifesting as mild illness. Chest x-ray showed bilateral non-homogeneous peri-hilar opacities with air bronchogram in 19 (61%) children. Seven (22%) children required admission to ICU, 6 (20%) required oxygen therapy and 1 required noninvasive ventilation. Two children had developed hypotension requiring inotropes. No mortality was observed in the current study. Conclusions: H1N1 Influenza is still causing significant morbidity among children, especially in those with malnutrition and preexisting medical illness.

Immunogenicity and safety of a Trivalent Influenza HA vaccine in Indonesian infants and children

IntroductionHigh rate of influenza infection in children made influenza vaccination strongly recommended for all person aged >6 months in Indonesia. Bio Farma Trivalent Influenza HA (Flubio®) vaccine has been used in adolescents and adults, resulted in increased seroconversion, seroprotection rates and geometric mean titer (GMT). However, no data is available regarding its efficacy and safety in children. This study aimed to assess the immunogenicity and safety of Flubio® vaccine in infants and children. Materials and methodsThis was a phase II, open-labeled, clinical trial conducted on healthy children aged 6 month-11 years, vaccinated with 1 or 2 doses of Influenza HA vaccine, with a 28-day interval. Flubio® vaccine composed of A/California/7/2009 (H1N1) pandemic 09, A/Texas/50/2012 (H3N2), and B/Massachusetts/2/2012 strain. This study was held at East Jakarta, Indonesia from May until July 2014. A Total of 405 subjects were included and divided into three groups: A(6–35 months), B(3–8 years), and C(9–11 years). Antibody titer was measured at visit V1 (Day 0), V2 (28 days/+7days after the first dose) and V3 (28 days/+7days after second dose). The seroprotection and seroconversion rates were assessed. Safety was assessed up to 28 days following each dose. ResultsA total of 404 subjects completed the study. After vaccination, all subjects achieved seroprotection and increased seroconversion rates, with post-vaccination antibody titer of ≥1:40 HI for all strains. The GMT also increased significantly. Within 30 min after vaccination, 14.6% and 2% had local and systemic reactions; meanwhile, between 30 min to 72 h after vaccination, 35.1% and 13.6% subjects had local and systemic reactions, respectively. Most reactions were mild. No serious adverse event (SAE) was reported related to vaccine. ConclusionFlubio® (Influenza HA Trivalent) vaccine is immunogenic and safe for children aged 6 months-11 years.Trial Registration: The trial is registered at the US National Institutes of Health (ClinicalTrials.gov) #NCT02093260.

Analysis of Clinical Manifestations and Laboratory Findings in Children with Influenza B-Associated Myositis: A Single Center Study.

BackgroundInfluenza-associated myositis (IAM) is a rare and poorly recognized complication of influenza infection in children, and is characterized by acute onset of severe pain in the lower extremities and a refusal to ambulate walk. We sought to understand the association between IAM and influenza B infection and to investigate its clinical and laboratory characteristics in affected children.MethodsInfluenza B-associated myositis (IBAM) cases diagnosed in the pediatrics department of Wonkwang University Hospital from January 2010 and March 2016 were analyzed retrospectively.ResultsMedical records of affected children were examined, and clinical characteristics and laboratory findings were recorded. Of the 536 children diagnosed with influenza B infection, 47 children complained of bilateral calf pain with or without gait disturbance. All children exhibited elevated serum aspartate aminotransferase (AST) level. The median serum creatine kinase (CK) and lactate dehydrogenase (LDH) levels, reportedly elevated in myositis, were 2,597 IU/L and 678 IU/L, respectively. While the immunofluorescence test results were negative for some patients, the polymerase chain reaction test results indicated influenza B infection in all 47 children. At the time of hospital discharge, the patients' symptoms had resolved, and their CK levels had improved.ConclusionIBAM was generally benign and short, and although the blood AST, CK, and LDH levels were markedly high, the erythrocyte sedimentation rate and C-reactive protein levels were normal. Further, the duration of IBAM symptoms correlated with the duration of fever. The IBAM-associated clinical and laboratory findings are highly characteristic and may allow its rapid diagnosis during the influenza season.

Single radial haemolysis compared to haemagglutinin inhibition and microneutralization as a correlate of protection against influenza A H3N2 in children and adolescents

BackgroundSerum antibodies are often used as correlates of protection for influenza. Three commonly used serological assays for detecting influenza‐specific serum antibodies are single radial haemolysis (SRH), haemagglutinin inhibition (HAI) and microneutralization (MN). However, here are limited data on SRH as well as HAI and MN as correlates of protection against influenza in children and adolescents. There are also limited data that compare SRH to HAI and MN.ObjectivesWe sought primarily to understand how SRH titres correlate to protection against influenza infection in children and adolescents. We also compare SRH to HAI and MN.MethodsOf 732 healthy Hutterite children and adolescents aged between 3 and 15 years were enrolled from Saskatchewan and Alberta, Canada, in the 2008‐2009 flu season. Blood samples were drawn from participants at baseline and between 3 and 5 weeks post‐vaccination. Serum antibodies against seasonal H3N2 influenza were measured by SRH, HAI and MN assays.ResultsThe estimates of protective efficacy fluctuated when the cut‐off SRH values increased. The correlation between HAI and SRH titres was 0.53 (P<.01); between MN and SRH 0.82 (P<.01); and between HAI and MN 0.50 (P<.01). Sixteen per cent of participants had SRH titres below the detection limit, compared to 7% and 34% for the MN and HAI assays.Conclusions SRH had the worst correlation with protection against seasonal H3N2 in children and adolescents compared to MN and HAI. SRH, HAI and MN titres were significantly correlated with each other. SRH was less sensitive than MN but more sensitive than HAI.

An Assessment of the Validity of the Comprehensive Severity Index (CSI) as a Measure of Severity of Influenza Infection in Children

An Assessment of the Validity of the Comprehensive Severity Index (CSI) as a Measure of Severity of Influenza Infection in Children

Co-colonization by Streptococcus pneumoniae and Staphylococcus aureus in the throat during acute respiratory illnesses.

Pneumonia due to either Streptococcus pneumoniae (Sp) or Staphylococcus aureus (Sa) accounts for most mortality after influenza and acute respiratory illness (ARI). Because carriage precedes infection, we estimated Sp and Sa carriage to examine the co-colonization dynamics between Sp, Sa and respiratory viruses in the presence of ARI in the oropharynx. We tested oropharyngeal specimens of community subjects (aged ⩾2 years) with ARI for the presence of influenza A and B, 11 other common respiratory viruses, Sp and Sa, using real-time PCR. A total of 338 participants reported 519 ARI episodes of which 119 (35%) carried Sp, 52 (13%) carried Sa and 25 (7%) carried both. Thirty-five subjects tested positive for influenza, of which 14 (40%) carried Sp and six (17%) carried Sa, significantly more than in the influenza-negative group (P = 0·03 and P = 0·04, respectively). In subjects infected by any virus compared to those with no virus, Sp carriage (39·2% vs. 27·9%, P = 0·03) but not Sa carriage (11·6% vs. 14%, P = 0·6) was more frequent. For children, when Sa was present, Sp carriage tended to be less frequent than expected given the presence of viral infection, but not significantly [observed relative risk 1·14, 95% confidence interval (CI) 0·4-3·1; with a relative excess risk due to interaction of -0·11]. Independent of age, Sp carriers were more likely to return that season with subsequent ARI (odds ratio 2·14, 95% CI 1·1-4·3, P = 0·03). Both Sp and Sa carriage rates in the oropharynx increase during influenza infection in children. However, no negative interaction between Sp and Sa was observed. Sp carriers are more likely to suffer subsequent ARI episodes than non-carriers.