Technical report: Reduction of the influenza burden in children

Influenza in Infants Born to Women Vaccinated During Pregnancy

BACKGROUND

Infants <6 months old with influenza are at risk for adverse outcomes. Our objective was to compare influenza outcomes in infants <6 months old born to women who did and did not report influenza vaccine during pregnancy.

METHODS

The study included all women who delivered from 12/2005 to 3/2014 at Intermountain facilities and their infants. Influenza outcomes included infant influenza-like illness (ILI), laboratory-confirmed influenza, and influenza hospitalizations.

RESULTS

The cohort included 245 386 women and 249 387 infants. Overall, 23 383 (10%) pregnant women reported influenza immunization. This number increased from 2.2% before the H1N1 pandemic to 21% postpandemic (P < .001). A total of 866 infants <6 months old had ≥1 ILI encounter: 32 (1.34/1000) infants born to women reporting immunization and 834 (3.70/1000) born to women who did not report immunization (relative risk [RR] 0.36; 95% confidence interval [CI], 0.26-0.52; P < .001). A total of 658 infants had laboratory-confirmed influenza: 20 (0.84/1000) born to women reporting immunization and 638 (2.83/1000) born to unimmunized women (RR 0.30; 95% CI, 0.19-0.46; P < .001). A total of 151 infants with laboratory-confirmed influenza were hospitalized: 3 (0.13/1000) born to women reporting immunization and 148 (0.66/1000) born to unimmunized women (RR 0.19; 95% CI, 0.06-0.60; P = .005).

CONCLUSIONS

Self-reported influenza immunization during pregnancy was low but increased after the H1N1 pandemic. Infants born to women reporting influenza immunization during pregnancy had risk reductions of 64% for ILI, 70% for laboratory-confirmed influenza, and 81% for influenza hospitalizations in their first 6 months. Maternal influenza immunization during pregnancy is a public health priority.

Safety and Immunogenicity of Full-Dose Trivalent Inactivated Influenza Vaccine (TIV) Compared With Half-Dose TIV Administered to Children 6 Through 35 Months of Age

BACKGROUND

Children 6 through 35 months of age are recommended to receive half the dose of influenza vaccine compared with older children and adults.

METHODS

This was a 6-site, randomized 2:1, double-blind study comparing full-dose (0.5 mL) trivalent inactivated influenza vaccine (TIV) with half-dose (0.25 mL) TIV in children 6 through 35 months of age. Children previously immunized with influenza vaccine (primed cohort) received 1 dose, and those with no previous influenza immunizations (naive cohort) received 2 doses of TIV. Local and systemic adverse events were recorded. Sera were collected before immunization and 1 month after last dose of TIV. Hemagglutination inhibition antibody testing was performed.

RESULTS

Of the 243 subjects enrolled (32 primed, 211 naive), data for 232 were available for complete analysis. No significant differences in local or systemic reactions were observed. Few significant differences in immunogenicity to the 3 vaccine antigens were noted. The immune response to H1N1 was significantly higher in the full-dose group among primed subjects. In the naive cohort, the geometric mean titer for all 3 antigens after 2 doses of TIV were significantly higher in the 12 through 35 months compared with the 6 through 11 months age group.

CONCLUSIONS

Our study confirms the safety of full-dose TIV given to children 6 through 35 months of age. An increase in antibody responses after full- versus half-dose TIV was not observed, except for H1N1 in the primed group. Larger studies are needed to clarify the potential for improved immunogenicity with higher vaccine doses. Recommending the same dose could simplify the production, storage, and administration of influenza vaccines.

Influenza virus surveillance among young children in São Paulo, Brazil: the impact of vaccination

This study assessed the presence of influenza virus among young children and the coverage of vaccination from 2010 to 2012 in São Paulo, Brazil. Our results demonstrated a lower rate of influenza detection and a predominance of influenza B. A decrease of coverage vaccination through the surveillance periods was observed.

Socio-economic burden of influenza among children younger than 5 years in the outpatient setting in Suzhou, China

Background

The disease burden of children with laboratory-confirmed influenza in China has not been well described. The aim of this study was to understand the epidemiology and socio-economic burden of influenza in children younger than 5 years in outpatient and emergency department settings.

Methods

A prospective study of laboratory-confirmed influenza among children presenting to the outpatient settings in Soochow University Affiliated Children's Hospital with symptoms of influenza-like illness (ILI) was performed from March 2011 to February 2012. Throat swabs were collected for detection of influenza virus by reverse transcription polymerase chain reaction assay. Data were collected using a researcher administered questionnaire, concerning demographics, clinical characteristics, direct and indirect costs, day care absence, parental work loss and similar respiratory illness development in the family.

Results

Among a total of 6,901 children who sought care at internal outpatient settings, 1,726 (25%) fulfilled the criteria of ILI and 1,537 were enrolled. Influenza was documented in 365 (24%) of enrolled 1,537 ILI cases. Among positive patients, 52 (14%) were type A and 313 (86%) were type B. About 52% of influenza outpatients had over-the-counter medications before physician visit and 41% visited hospitals two or more times. Children who attended daycare missed an average of 1.9 days. For each child with influenza-confirmed disease, the parents missed a mean of 1.8 work days. Similar respiratory symptoms were reported in 43% of family contacts of influenza positive children after onset of the child's illness. The mean direct and indirect costs per episode of influenza were $123.4 for outpatient clinics and $134.6 for emergency departments, and $125.9 for influenza A and $127.5 for influenza B.

Conclusions

Influenza is a common cause of influenza-like illness among children and has substantial socio-economic impact on children and their families regarding healthcare seeking and day care/work absence. The direct and indirect costs of childhood influenza impose a heavy financial burden on families. Prevention measures such as influenza vaccine could reduce the occurrence of influenza in children and the economic burden on families.

Influenza vaccination options to prevent hospitalization

BACKGROUND

Vaccination of children against influenza remains a controversial topic despite the substantial morbidity caused by this infection.

OBJECTIVE

To estimate the effect of three different vaccination strategies on preventing hospitalization due to influenza.

METHODS

A retrospective chart review was conducted of all children admitted to a tertiary health care centre who tested positive for influenza during three consecutive influenza seasons.

RESULTS

The final analysis included 208 cases with an age range of five days to 16.1 years. Seventy-six children were considered 'high-risk' and 132 were considered 'previously healthy'. Length of stay (LOS) ranged from one day to 46 days with a mean of 6.3 days. The mean LOS was 8.6 days for children with risk factors and 4.9 days for those without risk factors. The number of preventable influenza admissions was determined over three years and averaged over one year for the three vaccination strategies. A universal strategy of vaccinating all previously healthy and high-risk children over six months of age would have prevented 118 admissions. Using a selective strategy of vaccinating only children over six months of age with risk factors and a third strategy of vaccinating only two- to six-month-old infants would have prevented 58 and 55 admissions, respectively.

CLINICAL IMPLICATION

Use of the universal vaccination strategy would have prevented over one-half of the influenza admissions, which was over twice that of targeted vaccination. Until the challenges of implementing universal vaccination are fully understood, targeted vaccination remains an acceptable alternative.

A Phase III evaluation of immunogenicity and safety of two trivalent inactivated seasonal influenza vaccines in US children

BACKGROUND

This study (NCT00383123) compared the immunogenicity and safety of 2 trivalent inactivated influenza vaccines: Fluarix [GlaxoSmithKline (study vaccine)] and Fluzone [Sanofi Pasteur (control vaccine)] in children 6 months to <18 years.

METHODS

Children, stratified by age and randomized, received either study (N = 2115) or control vaccine (N = 1210) at day 0 (and day 28 for previously unvaccinated children younger than 9 years). Children 6 months to <5 years comprised the according-to-protocol (ATP) cohort for immunogenicity, whereas the reactogenicity/safety group included all children 6 months to <18 years. The study aimed to demonstrate immunologic noninferiority of study vaccine versus control vaccine.

RESULTS

For children 6 months to <5 years, the predefined noninferiority criteria were not reached, mainly due to the differences in immune response in children 6 months to <3 years with no influenza vaccination history. All reactogenicity/safety endpoints were within the same range in both vaccine groups.

CONCLUSIONS

The study vaccine demonstrated a good safety and reactogenicity profile; however, it did not meet the predefined noninferiority criteria in children 6 months to <5 years. The study vaccine was as immunogenic as the control vaccine in children aged 3 to <5 years.

Pandemic Influenza: Potential Contribution to Disease Burden

Records of disease outbreaks resembling influenza date to the writings of Hippocrates (fifth century BPE). Since then, influenza has afflicted humans around the globe. The most severe (“Spanish Flu” 10.1007/978-0-387-78665-0_6287) of three major outbreaks of the twentieth century killed approximately 20–50 million people worldwide. More recently, the global spread of highly pathogenic bird-adapted strain H5N1 is considered a significant pandemic threat. Since 2003, a total of 379 cases and 239 deaths have been reported. This chapter provides an overview of the genetic characteristics of the virus that elucidate its ability to continuously evade a host’s immune system; it describes some of the approaches used to quantify the burden of influenza and discusses their implications for the prevention and containment of future pandemics. The preliminary findings of the studies discussed here suggest that influenza-related burden is highly underestimated in tropical and subtropical regions of the world. This implicates that proper assessment of influenza-related morbidity and mortality worldwide is essential in planning and allocating resources to protect against what could be one of mankind’s most devastating challenges. A summary of learned lessons from past influenza pandemics are described and new intervention strategies aim at curtailing a future pandemic are discussed. More importantly, however, is the discussion of today’s challenges such as antiviral resistance, limited resources in a world that is globally connected and the imminent gap between the capacity (resources available) of developed and developing parts of the world to respond to a pandemic.

Influenza-related hospitalisations in children

AIM

To describe the disease burden, clinical pattern and outcome of influenza-related hospitalisations in children.

METHODS

This is a retrospective study carried out in a regional hospital in Hong Kong. Children hospitalised with established diagnosis of influenza infection from January to June of 2005 were studied. Length of hospitalisation, demographic characteristics, symptoms, clinical diagnosis and complications of influenza infection were analysed.

RESULTS

Influenza A infection accounted for 93.5% of these hospitalisations. Children less than 5 years of age comprised 70% of admission. Highest rate of admission occurred in May and April. One fourth of emergency admission during the study period and over 70% in the peak season was a result of influenza-related illness. Underlying medical disease was observed in 14.6% of children. Mean duration of hospitalisation was 3.0 days. Fever was the commonest presenting symptoms. Fever lasting for 7 days or more was observed in one-fifth of patients. Respiratory tract diseases (upper and lower) were the most frequent non-neurological diagnosis. Febrile convulsion was the complication observed in 27.6% of admission. One patient died as a result of acute necrotising encephalopathy.

CONCLUSION

Influenza contributed to heavy health-care burden. Mortality was rare but did occur. Hospitalisations occurred in both healthy children and those with underlying chronic illness. Young children played an important role in such hospitalisations. Means to prevent influenza-associated morbidity and mortality especially among young children are needed.

The effect of rapid diagnostic testing for influenza on the reduction of antibiotic use in paediatric emergency department

AIM

To determine the influence of rapid diagnosis of influenza on antibiotic prescribing to children presenting with influenza-like illness in the emergency department in a inner city hospital in Istanbul, Turkey.

METHODS

Patients aged 3 to 14 years presenting to an urban children's teaching hospital emergency department were screened for fever and cough, coryza, myalgias and/or malaise. After obtaining informed consent, patients were allocated into two groups. Group 1: patients were prescribed antibiotics after only physical examination; or Group 2: patients were prescribed antibiotics after rapid influenza testing. Nasopharyngeal swabs obtained from all patients were immediately tested in a single-blind manner with Influenza A/B Rapid Test(R) for influenza A and B.

RESULTS

A total of 97 patients were enrolled, and 33 (34%) of these tested positive for influenza. Although frequency of positive results for influenza between the groups was similar (36% vs 32%, respectively), patients in Group 2 were less likely to be prescribed antibiotics when compared to those in Group 1 (32% vs 100%, respectively, p < 0.0001).

CONCLUSION

Rapid diagnosis of influenza in the paediatric emergency department may allow a significant reduction in the over-prescription of antibiotics.

Influenza virus infection and the risk of serious bacterial infections in young febrile infants

OBJECTIVE

We aimed to determine the risk of SBIs in febrile infants with influenza virus infections and compare this risk with that of febrile infants without influenza infections.

PATIENTS AND METHODS

We conducted a multicenter, prospective, cross-sectional study during 3 consecutive influenza seasons. All febrile infants <or=60 days of age evaluated at any of 5 participating pediatric EDs between October and March of 1998 through 2001 were eligible. We determined influenza virus status by rapid antigen detection. We evaluated infants with blood, urine, cerebrospinal fluid, and stool cultures. Urinary tract infection (UTI) was defined by single-pathogen growth of either >or=5 x 10(4) colony-forming units per mL or >or=10(4) colony-forming units per mL in association with a positive urinalysis. Bacteremia, bacterial meningitis, and bacterial enteritis were defined by growth of a known bacterial pathogen. SBI was defined as any of the 4 above-mentioned bacterial infections.

RESULTS

During the 3-year study period, 1091 infants were enrolled. A total of 844 (77.4%) infants were tested for the influenza virus, of whom 123 (14.3%) tested positive. SBI status was determined in 809 (95.9%) of the 844 infants. Overall, 95 (11.7%) of the 809 infants tested for influenza virus had an SBI. Infants with influenza infections had a significantly lower prevalence of SBI (2.5%) and UTI (2.4%) when compared with infants who tested negative for the influenza virus. Although there were no cases of bacteremia, meningitis, or enteritis in the influenza-positive group, the differences between the 2 groups for these individual infections were not statistically significant.

CONCLUSIONS

Febrile infants <or=60 days of age with influenza infections are at significantly lower risk of SBIs than febrile infants who are influenza-negative. Nevertheless, the rate of UTI remains appreciable in febrile, influenza-positive infants.

Use of antibiotics in children hospitalized with community-acquired, laboratory-confirmed influenza

Many children with influenza are treated with antibiotics. In this report, we describe the rate and indications for antibacterial use in children hospitalized with influenza. A total of 333 of 729 (46%) patients received >2 days of treatment with antibacterial medications, of whom 36% did not have an apparent indication for therapy.

Availability of trivalent inactivated influenza vaccine to parents of neonatal intensive care unit patients and its effect on the healthcare worker vaccination rate

BACKGROUND

Trivalent inactivated influenza vaccine (TIV) is indicated for healthcare workers (HCWs); however, the vaccination rate in this population is estimated at 35%. We implemented a program for the administration of TIV, targeted at parents of neonatal intensive care unit (NICU) patients.

OBJECTIVE

To determine the effect of availability of TIV to parents in the NICU on HCW vaccination rates.

DESIGN

Questionnaire survey after an intervention-based study.

SETTING

Tertiary-care neonatal intensive care unit.

PARTICIPANTS

Physicians, nurses, and other NICU-based staff.

METHODS

For the 2005-2006 influenza season, parents of NICU patients were screened and administered TIV, if informed consent was obtained. As a consequence, TIV was available 20 hours/day to all staff. Previous vaccination history and comorbidities in HCWs were also assessed.

RESULTS

Of 120 neonatal HCWs, 112 (93%) were screened during the 2005-2006 season; 80 (67%) were vaccinated, compared with 49 (41%) prior to the implementation of this program (P < .03, by Student's t test); 54 (45% of the study population, which includes senior neonatologists, fellow and resident physicians, nurses, respiratory therapists, X-ray technicians and clerical staff) received TIV in the NICU, compared with the 17 (14%) of 120 HCWs the previous year; and 20 (46%) of 43 HCWs of the nursing staff were vaccinated in the NICU, whereas only 3 (7%) of 43 HWCs were vaccinated outside the unit. Attending physicians had the lowest vaccination rate, and most cited efficacy and/or side effects in their deferral. Nurses most often refused influenza vaccination because they had a fear of injection.

CONCLUSIONS

Administration of TIV in the NICU is an effective means of increasing the vaccination rate among neonatal HCWs. To increase compliance with vaccination, educational efforts for nurses should emphasize the possibility of viral transmission to neonates as motivation for vaccination. Physician-directed efforts should include tolerability of vaccine side effects. Live attenuated influenza vaccine, administered intranasally, should be considered to increase vaccination rates among NICU nurses.

Administration of tetanus, diphtheria, and acellular pertussis vaccine to parents of high-risk infants in the neonatal intensive care unit

OBJECTIVE

Tetanus, diphtheria, and acellular pertussis vaccination is recommended for adults who are in contact with infants who are younger than 12 months and in the NICU. The objective of this study was to determine the feasibility of tetanus, diphtheria, and acellular pertussis vaccine administration to parents in a tertiary care, level III NICU and to measure its effect on vaccination rates among parents of this high-risk population.

METHODS

For a 4-month period from July to October 2007, all parents of admitted patients were informed of the risks and benefits of tetanus, diphtheria, and acellular pertussis vaccine by placing an information letter at their infant's bedside. All staff were educated about the dangers of pertussis infection and instructed to reinforce the need to obtain vaccination. Immunization was available for 20 hours per day at no cost. Student's t tests were used for data analysis.

RESULTS

During the study period, 352 children (598 eligible parents) were admitted to the NICU at gestational ages ranging from 23 to 42 weeks, and 495 (82.8%) parents were offered the vaccine. Overall vaccination rate was 86.9% (430 parents) of the screened population. Fifty-five (11.1%) parents in the screened cohort refused vaccination, predominately citing pertussis as an insignificant health threat or disbelief in vaccination. There were no differences in vaccination rate on the basis of parental age. No allergic reactions to vaccination were observed. The 54 infants whose parents were not offered vaccine had a significantly shorter length of stay, higher birth weight, and higher gestational age than parents who were offered vaccine.

CONCLUSIONS

Administration of tetanus, diphtheria, and acellular pertussis vaccine in the NICU is an effective means of increasing vaccination rates of parents of this population. Logistic barriers persist when implementing this program for infants with a short (<3-day) length of stay.

Correlation of cellular immune responses with protection against culture-confirmed influenza virus in young children

The highly sensitive gamma interferon (IFN-gamma) enzyme-linked immunosorbent spot (ELISPOT) assay permits the investigation of the role of cell-mediated immunity (CMI) in the protection of young children against influenza. Preliminary studies of young children confirmed that the IFN-gamma ELISPOT assay was a more sensitive measure of influenza memory immune responses than serum antibody and that among seronegative children aged 6 to <36 months, an intranasal dose of 10(7) fluorescent focus units (FFU) of a live attenuated influenza virus vaccine (CAIV-T) elicited substantial CMI responses. A commercial inactivated influenza virus vaccine elicited CMI responses only in children with some previous exposure to related influenza viruses as determined by detectable antibody levels prevaccination. The role of CMI in actual protection against community-acquired, culture-confirmed clinical influenza by CAIV-T was investigated in a large randomized, double-blind, placebo-controlled dose-ranging efficacy trial with 2,172 children aged 6 to <36 months in the Philippines and Thailand. The estimated protection curve indicated that the majority of infants and young children with >or=100 spot-forming cells/10(6) peripheral blood mononuclear cells were protected against clinical influenza, establishing a possible target level of CMI for future influenza vaccine development. The ELISPOT assay for IFN-gamma is a sensitive and reproducible measure of CMI and memory immune responses and contributes to establishing requirements for the future development of vaccines against influenza, especially those used for children.

Prevention of influenza: recommendations for influenza immunization of children, 2007-2008

The American Academy of Pediatrics recommends annual influenza immunization for all children with high-risk conditions who are 6 months of age and older, for all healthy children ages 6 through 59 months, for all household contacts and out-of-home caregivers of children with high-risk conditions and of healthy children younger than 5 years, and for all health care professionals. To more fully protect against the morbidity and mortality of influenza, increased efforts are needed to identify and immunize all children at high risk and all healthy children ages 6 through 59 months and to inform their parents when annual immunizations are due. Previously unimmunized children who are at least 6 months of age but younger than 9 years should receive 2 doses of influenza vaccine, given 1 month apart, beginning as soon as possible on the basis of local availability during the influenza season. If children in this cohort received only 1 dose for the first time in the previous season, it is recommended that 2 doses be administered in the current season. This recommendation applies only to the influenza season that follows the first year that a child younger than 9 years receives influenza vaccine. A child who then also fails to receive 2 doses the next year should be given only 1 dose per year from that point on. Influenza vaccine should also continue to be offered throughout the influenza season, even after influenza activity has been documented in a community. On the basis of global surveillance of circulating virus strains, the influenza vaccine may change from year to year; indeed, 1 of the 3 strains in the 2007-2008 vaccine is different from the previous year's vaccine. All health care professionals, influenza campaign organizers, and public health agencies should develop plans for expanding outreach and infrastructure to immunize all children for whom influenza vaccine is recommended. Appropriate prioritization of administering influenza vaccine will also be necessary when vaccine supplies are delayed or limited. Because the influenza season often extends into March, immunization against influenza is recommended to continue through late winter and early spring. Lastly, it is recommended that for the 2007-2008 season, and likely beyond, health care professionals do not prescribe amantadine or rimantadine for influenza treatment or chemoprophylaxis, because widespread resistance to these antiviral medications now exists among influenza A viral strains. However, oseltamivir and zanamivir can be prescribed for treatment or chemoprophylaxis, because influenza A and B strains remain susceptible.

Administration of inactivated trivalent influenza vaccine to parents of high-risk infants in the neonatal intensive care unit

OBJECTIVE

Infants who are younger than 6 months and have influenza demonstrate significant morbidity and mortality. Trivalent inactivated influenza vaccine is indicated for parents and household contacts of these infants; however, the influenza vaccination rate in this population is estimated at 30%. The objective of this study was to determine the feasibility of trivalent inactivated influenza vaccine administration to parents in a tertiary-care, level III NICU and measure the effect of this program on vaccination rates among parents of this high-risk population.

METHODS

For a 4-month period during influenza season, all parents of admitted patients were informed of the risks and benefits of trivalent inactivated influenza vaccine by placing an information letter at their infant's bedside. All staff were educated about the dangers of influenza and instructed to reinforce the need to obtain vaccination. Parents were screened, provided medical consent, and, when eligible, were immunized at their infant's bedside.

RESULTS

During the study period, 158 children (273 parents) were admitted to the NICU with gestational ages ranging from 24 to 41 weeks; 220 parents (130 infants) were offered the vaccine, and 40 parents received the vaccine from their obstetrician. Overall vaccination rate was 95% (209 parents). A total of 23% of the parent population had never received trivalent inactivated influenza vaccine, despite having previous indications for immunization (smoking, asthma, or other children younger than 23 months, the indicated age for parental vaccination at the time of this study); 75% of the population received trivalent inactivated influenza vaccine for the first time. The 28 infants whose parents were not offered vaccine spent <72 hours in the NICU.

CONCLUSIONS

Administration of trivalent inactivated influenza vaccine in the NICU is an effective means of increasing vaccination rates in parents of this population. In addition, the improved access and convenience allow for an increase in first-time vaccination of parents who were previously eligible to receive trivalent inactivated influenza vaccine but were never immunized.

Computer-based multivariate economic analysis of neonatal-intensive-care-unit-based influenza vaccine administration to parents in a low-socio-economic, urban setting

OBJECTIVE

Trivalent inactivated influenza vaccine has been shown to reduce the number of influenza-related outpatient visits and hospitalizations of children up to 24 months of age. The American Academy of Pediatrics, Centers for Disease Control, and Advisory Committee on Immunization Practices recommend that the influenza vaccine be administered to the first-person contacts of infants less than 6 months of age. However, the economic implications of increasing immunization rates by using the neonatal intensive care unit (NICU) as an arena to capture the parents of these infants has not been fully evaluated. We sought to examine the direct and indirect costs of a program to administer the influenza vaccine to parents in the NICUs of a cohort of tertiary-care units primarily serving a low socioeconomic population.

METHODS

The probabilities of infants being hospitalized because of infection from contact and of the efficacy of prophylaxis used in the present study were based on published results where possible, with an estimated 10% reduction in hospitalization of patients whose parents had received the vaccine. Variables in the 3- and 4-tiered analyses included chronic lung disease status, estimation if patients had siblings, vaccination status of siblings, seroconversion rate of vaccine, and parental vaccination status. Two thousand six hundred and thirty-two patients were analyzed using 2003 admission data from the New York City Regional Perinatal Center, which encompasses 11 level III NICUs. Hospitalization costs, indirect costs, and outpatient costs were assessed using previously published standard calculations.

RESULTS

On the basis of this computer model, costs were $188 per patient per influenza season, including $6.80 per patient in outpatient costs. Administration of an NICU-based influenza vaccine increased costs to $200 per patient per influenza season, but decreased outpatient costs to $1.40 per patient. For cost savings to equal costs of vaccine administration, there must be either a 20% reduction in influenza hospitalizations of NICU patients or an increase in the sample size per influenza season to 4000 patients.

CONCLUSIONS

The cost of administration of the influenza vaccine to parents of NICU patients is higher than the financial burden of influenza in this population as long as the sibling immunization rate remains low. Cost savings do not occur until the treated cohort increases to 4000 patients or the incidence of lung disease in this population increases. Further studies are needed to validate the cost savings of this mode and more accurately assess the financial savings.

Influenza burden in febrile infants and young children in a pediatric emergency department

BACKGROUND

In France, epidemiologic data in children in ambulatory settings are scarce. We aimed to measure the burden of influenza in young children.

METHODS

Febrile children younger than 36 months were consecutively recruited in a pediatric emergency department during the 2002 epidemic peak. Virology analysis and follow-up were systematic.

RESULTS

During calendar weeks 3 to 6, 2002, 575 children were recruited; 49% were positive: A/H3N2 in 44% and B in 5%. Prevalence rate was 57% in 12- to 35-month-old children and 39% in infants younger than 12 months. The main clinical pictures were nonrespiratory in one third of them. One of 8 patients had a complication. One of 10 patients was hospitalized, and the estimated specific hospitalization rate for the study period was 237 of 100,000 in the general population among infants younger than 12 months. Forty-two percent of children (n = 110) were prescribed antibiotics and at least 34% of them were inappropriate (n = 89). Median length of disease was 8 days, and 25% of the children had not fully recovered by day 11. Only one child had been previously vaccinated of 65 with chronic conditions. Both epidemic strains were covered by the vaccine.

CONCLUSIONS

Health outcomes showed that influenza disease burden in young French children is similar to that observed in North America. An active vaccination strategy would have strongly reduced the burden of influenza and lowered antibiotic use. Continuous efforts are needed to reach requirements of our influenza vaccination policy.

Rationale for the administration of acellular pertussis vaccine to parents of infants in the neonatal intensive care unit

Pertussis infections in the United States are increasing as a consequence of waning immunity and increased surveillance. Those most at-risk of mortality include infants less than 6 months of age and premature infants. The 2006 immunization schedule emphasizes an adolescent pertussis booster at 12 years of age. However, of concern is the current generation of parents and grandparents who will still be un-immunized and therefore, available vectors of pertussis to vulnerable neonates. Given the proximity of parents to medical care in the Neonatal Intensive Care Unit (NICU), and the potential for severe disease in their children, NICU personnel should consider administration of acellular pertussis vaccine to parents of hospitalized infants.

Estimating the undetected burden of influenza hospitalizations in children

During the 2004-2005 influenza season two independent influenza surveillance systems operated simultaneously in three United States counties. The New Vaccine Surveillance Network (NVSN) prospectively enrolled children hospitalized for respiratory symptoms/fever and tested them using culture and RT-PCR. The Emerging Infections Program (EIP) and a similar clinical-laboratory surveillance system identified hospitalized children who had positive influenza tests obtained as part of their usual medical care. Using data from these systems, we applied capture-recapture analyses to estimate the burden of influenza related-hospitalizations in children aged<5 years. During the 2004-2005 influenza season the influenza-related hospitalization rate estimated by capture-recapture analysis was 8.6/10,000 children aged<5 years. When compared to this estimate, the sensitivity of the prospective surveillance system was 69% and the sensitivity of the clinical-laboratory based system was 39%. In the face of limited resources and an increasing need for influenza surveillance, capture-recapture analysis provides better estimates than either system alone.

A Bayesian dynamic model for influenza surveillance

The severe acute respiratory syndrome (SARS) epidemic, the growing fear of an influenza pandemic and the recent shortage of flu vaccine highlight the need for surveillance systems able to provide early, quantitative predictions of epidemic events. We use dynamic Bayesian networks to discover the interplay among four data sources that are monitored for influenza surveillance. By integrating these different data sources into a dynamic model, we identify in children and infants presenting to the pediatric emergency department with respiratory syndromes an early indicator of impending influenza morbidity and mortality. Our findings show the importance of modelling the complex dynamics of data collected for influenza surveillance, and suggest that dynamic Bayesian networks could be suitable modelling tools for developing epidemic surveillance systems.

Surveillance for influenza admissions among children hospitalized in Canadian immunization monitoring program active centers, 2003-2004

OBJECTIVES

Influenza is a common childhood infection that may result in hospitalization. Our objectives were to (1) determine characteristics of children hospitalized for influenza and disease manifestations and (2) obtain baseline data before implementation of new recommendations for routine immunization of young children and their caretakers against influenza.

METHODS

All of the children hospitalized with laboratory-confirmed influenza at 9 Canadian tertiary care hospitals during the 2003-2004 influenza season were identified from virology laboratory reports, and their charts were reviewed.

RESULTS

There were 505 children admitted because of influenza. Fifty-seven percent were < 2 years old. Previously healthy children accounted for 58% of all of the cases. Pulmonary and neurologic disorders were the most common underlying chronic conditions. Fever and cough were the most frequent manifestations. Seizures occurred in 9% of cases. Serious complications included myocarditis (2), encephalopathy (6), and meningitis (1). There were 3 influenza-related deaths. Mean duration of hospitalization was 5.3 days. Twelve percent of children required ICU admission, and 6% required mechanical ventilation. Antibiotic therapy was administered in 77% of cases, and 7% received anti-influenza drugs. Information on influenza vaccination was available for 84 of 154 children identified as vaccine candidates. Twenty two had received vaccine, but only 7 children had been fully immunized > 14 days before the onset of illness.

CONCLUSIONS

Healthy young children and children with chronic conditions are at risk for serious illness with influenza. Ongoing surveillance is needed to evaluate the impact of changing immunization recommendations on the burden of influenza illness in children.

Integrated molecular signature of disease: analysis of influenza virus-infected macaques through functional genomics and proteomics

Recent outbreaks of avian influenza in humans have stressed the need for an improved nonhuman primate model of influenza pathogenesis. In order to further develop a macaque model, we expanded our previous in vivo genomics experiments with influenza virus-infected macaques by focusing on the innate immune response at day 2 postinoculation and on gene expression in affected lung tissue with viral genetic material present. Finally, we sought to identify signature genes for early infection in whole blood. For these purposes, we infected six pigtailed macaques (Macaca nemestrina) with reconstructed influenza A/Texas/36/91 virus and three control animals with a sham inoculate. We sacrificed one control and two experimental animals at days 2, 4, and 7 postinfection. Lung tissue was harvested for pathology, gene expression profiling, and proteomics. Blood was collected for genomics every other day from each animal until the experimental endpoint. Gross and microscopic pathology, immunohistochemistry, viral gene expression by arrays, and/or quantitative real-time reverse transcription-PCR confirmed successful yet mild infections in all experimental animals. Genomic experiments were performed using macaque-specific oligonucleotide arrays, and high-throughput proteomics revealed the host response to infection at the mRNA and protein levels. Our data showed dramatic differences in gene expression within regions in influenza virus-induced lesions based on the presence or absence of viral mRNA. We also identified genes tightly coregulated in peripheral white blood cells and in lung tissue at day 2 postinoculation. This latter finding opens the possibility of using gene expression arrays on whole blood to detect infection after exposure but prior to onset of symptoms or shedding.

Estimating influenza hospitalizations among children

Two surveillance systems gave a better estimate of influenza hospitalizations in children <5 years of age than either system alone.

Although influenza causes more hospitalizations and deaths among American children than any other vaccine-preventable disease, deriving accurate population-based estimates of disease impact is challenging. Using 2 independent surveillance systems, we performed a capture-recapture analysis to estimate influenza-associated hospitalizations in children in Davidson County, Tennessee, during the 2003–2004 influenza season. The New Vaccine Surveillance Network (NVSN) enrolled children hospitalized with respiratory symptoms or fever and tested them for influenza. The Tennessee Emerging Infections Program (EIP) identified inpatients with positive influenza diagnostic test results through review of laboratory and infection control logs. The hospitalization rate estimated from the capture-recapture analysis in children <5 years of age was 2.4 per 1,000 (95% confidence interval 1.8–3.8). When NVSN estimates were compared with capture-recapture estimates, NVSN found 84% of community-acquired cases, EIP found 64% of cases in which an influenza rapid test was performed, and the overall sensitivity of NVSN and EIP for influenza hospitalizations was 73% and 38%, respectively.

Nuevas indicaciones de la vacuna inactivada antigripal en la población infantil (2004-2005)

Several epidemiological studies have indicated that, in all countries and in distinct epidemic years, the highest rates of influenza infection (between 15% and 42%) occur in the pediatric population, especially in school-aged children. Over various influenza seasons, the rates of annual outpatient visits attributable to influenza vary from 6-29% of children. Influenza and its complications have been reported to result in a 10-30% increase in the number of antibiotic courses prescribed to children during the influenza season. Current percentages of influenza vaccination in children are very low, although the hospitalization rates for infectious complications in children under 5 years are at least equal to those observed in individuals aged more than 65 years. The reasons for these low immunization rates are unknown, but many factors could be involved, especially the need for annual revaccination. In 2003 the Advisory Committee on Immunization Practices (ACIP) recommended influenza immunization only in children at high risk for influenza complications and in those living with someone in a high-risk group. However, they encouraged vaccination of all children aged 6-23 months old. After a review of various epidemiological studies, in 2004 both the ACIP and the American Academy of Pediatrics recommended systematic immunization of all healthy children within this age group. However, both institutions advise that before the routine introduction of influenza immunization in all children aged 6-23 months old, immunization programs in high-risk children need to be implemented.

Reducing the impact of viral respiratory infections in children

This article reviews the epidemiology and clinical aspects of the major viral causes of upper and lower respiratory tract disease in children. Particular emphasis is placed on prevention and control of viral disease through the use of vaccines and antiviral agents. Evolution of new viral pathogens, such as avian influenza virus and the SARS-CoV, are discussed.

Influenza vaccine in healthy children: a meta-analysis

We conducted a meta-analysis of 13 randomised clinical trials evaluating the efficacy of influenza vaccine in healthy children. Against culture-confirmed influenza the overall efficacy was 74% (95% confidence interval, CI, 57%-84%), 65% for inactivated and 80% for live-attenuated vaccine. Corresponding figures were 59% (95% CI 43%-71%), 63% and 54% for serologically-confirmed influenza, and 33% (95% CI 29%-36%), 33% and 34% for clinical illness. Influenza vaccine is effective in preventing laboratory-confirmed and clinical influenza in healthy children, with no clear difference between inactivated and live-attenuated vaccine. Data on infants and younger children were too scanty to allow separate assessment.

Pediatric influenza prevention and control

Global evaluation of influenza vaccination in children indicates that current recommendations are not followed. Most children at high risk for influenza-related complications do not receive the vaccine, and increased efforts are needed to protect them. Furthermore, immunizing healthy infants 6–23 months of age and their close contacts should be strongly encouraged. Vaccinations are recommended for children with recurrent acute otitis media or recurrent respiratory tract infections and possibly for healthy daycare and school-age children because of the potential socioeconomic implications of influenza. Issues that need to be addressed include educating physicians and parents concerning influenza-related illness and complications, cost-effectiveness and safety of licensed vaccines, adequate vaccine supply, and availability of intranasal products.

Optimizing long-term care by administration of influenza vaccine to parents of NICU patients

The neonatal intensive care unit (NICU) team has traditionally invested itself in maintaining the health of its patients upon discharge from high-acuity care. Historically, this has included the administration of vaccinations to the patients and more recently, Palivizumab--a monoclonal antibody directed against respiratory synctial virus (RSV). With increasing awareness of the ill-effects associated with influenza virus and recommendations those in close contact with high-risk infants receive the vaccine, the NICU may be an ideal arena to capture parents of high-risk infants for vaccination. This would potentially decrease exposure of the neonatal patient group to influenza virus and may decrease morbidity and mortality associated with the disease. NICUs should work in concert with their associated Departments of Obstetrics to immunize pregnant mothers when appropriate, educate parents regarding influenza and its potential effects in infants and offer influenza vaccine in-season to parents as part of comprehensive care.

Inactivated Influenza Virus Vaccines in Children

Healthy children aged < or =2 years have hospitalization rates during influenza periods 12 times those of older children and comparable to rates in the elderly population. In 2003, killed influenza vaccines were "recommended" for children with high-risk conditions and were "encouraged" for children aged 6-23 months. Studies involving several thousand children show that split-virus vaccines are safe and immunogenic in healthy children aged > or =6 months and in high-risk children. In children aged < or =9 years, 2 doses of vaccine are required initially to achieve maximum protection. Studies of children aged 6 months to 15 years show vaccine efficacies of 31%-91% against influenza A and 45% against influenza B. Among children attending day care, a reduction in the rate of acute otitis media of 32%-36% was demonstrated. Studies suggest that use of killed vaccines among children is cost-saving. In conclusion, the data show that killed influenza vaccines in children are safe, immunogenic, effective, and potentially cost-saving.

Are we ready for universal influenza vaccination in paediatrics?

Recent studies have suggested that paediatric influenza is a greater medical problem than usually thought because it can cause excess hospitalisations, medical visits, and antibiotic prescriptions even in healthy children, especially those under 2 years. Furthermore, influenza in otherwise healthy children may have substantial socioeconomic consequences for the children and their household contacts. These findings have led many experts to encourage the more widespread use of influenza vaccine in childhood. Although the immunogenicity of the available vaccines is good and they are safe, well-tolerated, and highly effective in preventing influenza and its complications, economic data support universal vaccination only when indirect effectiveness is considered. However, infants aged 6-23 months, children with recurrent acute otitis media or respiratory-tract infections, and healthy children attending day-care centres or elementary schools should be included among the paediatric groups requiring vaccination.

[Investigation of the reconsultation rate and pharmacoeconomic evaluation of period of influenza treatment by oseltamivir]

In the epidemic of influenza in fiscal 2002, there was a shortage in Japan of the anti-influenza virus medicine "oseltamivir". For this reason, many medical institutions were forced to shorten the treatment period with this medication. In this study, we compared the shorter oseltamivir treatment and the indicated 5-day course of treatment with the index for the reconsultation rate and medication dispensing fee from the viewpoint of pharmacoeconomics and clinical effect. Oseltamivir was prescribed for 2, 3 or 5 days for the treatment of influenza, and the rate of reconsultation, type of virus and age were analyzed. The total fees paid to a pharmacy for influenza treatment were also calculated for pharmacoeconomic evaluation. Two-day treated patients had a higher rate of reconsultation compared with the 3- and 5-day treatment groups. Analysis of patients by influenza virus type and age showed no significant difference in reconsultation rate. The total medication dispensing fees for 2-, 3- and 5-day treatment with oseltamivir were 4713, 4755 and 6520 yen, respectively, that of 5-day treatment being significantly higher. These results suggest that 2-day treatment by oseltamivir was significantly high in reconsultation rate, and 5-day treatment was significantly high in medication dispensing fee, so 3-day treatment of influenza by this medicine is the most suitable from the viewpoint of pharmacoeconomics and clinical effect.

Pneumonies communautaires et infection grippale

Children without chronic or serious medical conditions are at increased risk for hospitalization during influenza seasons, mainly with respiratory tract infections. But influenza virus infections frequently remain undiagnosed, even in hospitalized patients. We prospectively studied the rate of concomitant and preceding influenza infections in children hospitalized with a community acquired pneumonia (CAP).

POPULATION AND METHODS

All 1-15-year-old children with CAP requiring hospitalization between 1st April 2000 and 2002 had nasopharyngeal aspirate for viruses, immunofluorescence and serologies for respiratory pathogens. The peak of influenza IgG measured by complement fixation (CF) is transient, and a titer of 1/64 or more indicates an acute influenza infection in the preceding weeks. Children with chronic disease were excluded and a control group of patients from outpatient clinic was measured.

RESULTS

Among 33 previously healthy children (age 4.9 years, range 1.2-14 years), 8 had a pneumococcal pneumonia, 10 a pneumonia caused by Mycoplasma pneumoniae (MP), 1 by Chlamydia pneumonia, and 8 of unknown origin. In six patients immunofluorescence was positive: Respiratory Syncitial Virus, 2, Adenovirus, 1 and Influenza A, 3 (including a patient with concomitant MP infection). Thirteen of the 33 children (39.4%) had evidence of a recent influenza A infection with CF ab > or = 1/64: with pneumococcal pneumonia, 5/10 with MP pneumonia, 3/8 with unknown origin pneumonia, 9/13 of these previous influenza infections being clinically inapparent. Only 1/30 children of control group (3.3%) had CF ab > or = 1/64.

CONCLUSION

In this study, influenza infection is the direct cause of CAP of children in 12% of cases. In other children with CAP, 39.4% of patients had an influenza infection in the preceding weeks which leads to secondary infection caused by Streptococcus pneumoniae or by MP or other pathogens.

Burden of influenza in children: preliminary data from a pilot survey network on community diseases

BACKGROUND

The burden of influenza and its clinical presentation are both poorly documented in French children.

METHODS

To measure the prevalence of acute respiratory infections over two winters (2000 to 2001 and 2001 to 2002), we performed a prospective community survey of 0- to 15-year-olds (n = 11 500 and 40 000, respectively) through a network [Grippe et Infections Respiratoires Aiguës Pédiatriques (GIRAP)] of general practitioners and pediatricians. Influenza viruses were detected by antigen detection and culture from nasopharyngeal swabs. Data on the clinical presentation of children infected with influenza A/H1N1, A/H3N2 or B viruses were derived from standardized forms.

RESULTS

The prevalences of symptomatic acute respiratory infections were 28% and 27% for 2000 to 2001 and 2001 to 2002, respectively. In the winter of 2000 to 2001, a mild outbreak of influenza A/H1N1 affected 5.4% of the study population. The attack rates of influenza A/H1N1 were highest in children 5 to 15 years of age. In the winter of 2001 to 2002, influenza activity remained at a subepidemic level (5.9%; A/H3N2, 60%; B, 40%). The incidence of influenza A/H3N2 infections was highest in 2- to 4-year-old children, whereas influenza B strains were most frequently detected in children 4 to 10 years of age.

CONCLUSIONS

Despite subepidemic levels of influenza, the GIRAP network was able to detect influenza A or B viruses in 35 to 60% of the samples during the peak of influenza epidemic. The frequency of influenza virus excretion in children with mild clinical symptoms indicates that children are an important reservoir and source of transmission of this virus.

Risk factors associated with severe influenza infections in childhood: implication for vaccine strategy

Infections caused by influenza virus lead to an excess rate of hospitalization of children during winter months. Current recommendations for vaccination target only children >6 months who belong to specific risk groups.

OBJECTIVE

To identify possible benefits of universal influenza vaccination, this study aims to determine characteristics of children hospitalized at the Montreal Children's Hospital (MCH) because of an infection attributable to influenza virus as well as risk factors associated with hospitalization.

METHODS

We retrospectively reviewed records of all children with a laboratory-proven diagnosis of influenza seen at MCH between April 1, 1999, and April 1, 2002. Data were analyzed using the Student t test and logistic regression.

RESULTS

We identified 182 patients hospitalized because of influenza and 114 patients who were not. Admission diagnoses were suspected sepsis (31%), lower respiratory tract infections (27%), and asthma or bronchiolitis (15%). Mean age of hospitalized patients was 26.1 month (median: 12 months), which was similar to that of patients not hospitalized, and 34% were <6 months. Seventy percent of those hospitalized did not have any underlying medical disorder and only 18% (33) were vaccine candidates according to current recommendations. Of the latter, less than half had been vaccinated. Factors associated with hospitalization were age <12 months (odds ratio [OR]: 2.3; 95% confidence interval [CI]: 1.1-4.8), male gender (OR: 1.9; 95% CI: 1.0-3.7), dehydration (OR: 4.3; 95% CI: 1.2-16.0), and decreased oxygen saturation (OR: 32.1; 95% CI: 4.1-249).

CONCLUSIONS

Considering that the majority of children hospitalized for influenza do not belong to the specific risk groups targeted by current recommendations, and that one third are <6 months of age, the target population for vaccination needs to be reexamined. Extending vaccination to all young children, to additional high-risk groups, and to pregnant women has potential to reduce the impact of influenza on children.