Pilot study of influenza vaccine effectiveness in urban Australian children attending childcare.

BACKGROUND: Influenza outbreaks in the childcare setting are a significant cause of excess winter morbidity. This study explored methods of follow up and sample collection for a proposed randomised controlled trial of influenza vaccination in children attending childcare. METHODS: The study was conducted in four Sydney childcare centres during 2007. Healthy children aged 6-59 months eligible for vaccination were recruited in two centres, with another two acting as controls. Data on influenza-like illness (ILI: ≥37.8°C plus at least one respiratory symptom) occurrence were collected weekly. In those children with an ILI, parents were asked to collect nasal swabs and send via surface mail for viral polymerase chain reaction. Vaccine efficacy (VE) for ILI was estimated overall and for subgroups aged 6-23 and 24-59 months using the formula VE = 1 - relative risk (RR). RESULTS: Sixty-three per cent (151/238) of eligible children had parents give consent. Sixty-three children received influenza vaccine and 88 participated as controls. Of 26 specimens returned, a virus was detected in 18 (69%); none with influenza. Two symptomatic children had positive near-patient influenza tests in general practice (one a vaccine failure). The RR with 95% confidence interval in all children and those aged 6-23 months were less than one, 0.56 (0.32-1.02) and 0.46 (0.15-1.45), respectively. CONCLUSIONS: This study demonstrated the feasibility and utility of parent-collected and mailed respiratory specimens for VE research in the childcare setting. Two-thirds of parent-collected swabs proved positive for at least one virus. Finding ways to reduce reluctance of parents to submit samples could improve the representativeness of samples collected and the power of the study. No evidence was found for influenza VE, but point estimates were in the direction of protection.

The burden of influenza in children under 5 years admitted to the Children's Hospital at Westmead in the winter of 2006.

OBJECTIVE: Active surveillance to determine influenza disease burden in children admitted to hospital with influenza-like illness (ILI). METHODS: A prospective hospital-based cohort study conducted June-October 2006 in children <5 years hospitalised at The Children's Hospital at Westmead with ILI (fever and respiratory symptoms). Influenza and other viral infections were diagnosed either by antigen detection using immunofluorescence or nucleic acid amplification testing of nasopharyngeal aspirates. Data were collected using researcher-administered questionnaires. Main outcome measures include proportion of hospitalisations with influenza, vaccination and treatment, risk factors for influenza and associated medical and social burdens. RESULTS: Data on 275 children with ILI aged <5 years were analysed. Thirty-one (11%) children with ILI had influenza (22 had influenza A and 9 had influenza B). Thirty-five percent were under 6 months of age and 61% under 1 year. Twenty-nine percent of children with influenza A were born prematurely. The mean duration of hospital stay for influenza was 2.8 days (95% confidence interval 2.1-3.4) and 26% had a lumbar puncture. Although 68% received intravenous antibiotics, only 3% (one case) was given an antiviral. Eighty-four percent had visited their local doctor before admission and all came through the emergency department. On average, in one-third (32%) of families of children with influenza a parent developed, ILI during admission or soon after hospital discharge resulted in an average of 3.2 days of work absenteeism. Only 3.5% (7/199) of children older than 6 months with ILI received any influenza vaccination. CONCLUSIONS: Both the burden of influenza in childhood morbidity and its social impact are substantial. There is considerable room for improvement in both the prevention and early recognition (trigger treatment with antivirals) of influenza. Our data will inform decisions regarding the value of a universal influenza vaccine programme.

The burden of influenza in children.

PURPOSE OF REVIEW: This review summarizes recent studies that better address the burden of influenza from the medical and socioeconomic perspectives. The issue of influenza in children is one that has implications for future universal vaccination policies. RECENT FINDINGS: In the past, the burden of influenza in children was largely defined by hospital-based studies that quantify the incidence of influenza hospitalization and, consequently, the benefit of prevention in young children. The medical and the socioeconomic impact have been better appreciated recently with population-based studies because the great majority of children are managed as outpatients. Children with influenza may not have direct contact with medical services but still generate substantial costs in carer illness or work-day loss. Furthermore, the specificity offered by laboratory confirmation of influenza has enabled influenza to be separated from other respiratory viruses that may have confounded previous studies looking at the medical and economic costs of illness. SUMMARY: Better understanding of the burden of influenza in healthy children regarding hospitalization rates, outpatient medical visits, community-managed illness and socioeconomic impact on families and society exists; this has potential implications for universal vaccination policies under consideration.