Incidence of influenza and associated illness in children aged 0-19 years: a systematic review

Abstract

A systematic review was conducted to estimate the incidence of influenza and concomitant morbidity and mortality in children from 0 to 19 years (0-19 years). Medline was searched for observational studies and placebo or non-treated arms of experimental studies providing occurrence rates of laboratory-proven influenza illness. From the 2758 titles identified, 356 full papers were reviewed based on the abstract or title; after searching their reference lists an additional 16 papers were found. Finally 28 studies met our inclusion criteria, reporting a varying seasonal incidence of influenza of up to 46%. However, when analysing two long-term observational studies and averaging seasonal fluctuations, the overall incidence of influenza was found to range from 5% to 9.5% per year. Serious morbidity was seldom reported and no cases of mortality were found. Our review shows influenza as an infection with a moderate average incidence and a self-limiting character that is associated with mild morbidity and rare cases of mortality in children. This systematic review may be subject to two contrasting biases. First, the limited number of children reported in the literature with proven influenza infections would tend to under-represent the incidence of uncommon but serious complications such as death. Second, the preferential reporting of influenza outbreak seasons may over-estimate the importance of influenza. Future population based studies should focus on consecutive influenza seasons and capture indirect benefits of vaccinations such as interruption of transmission in the community so that preventive strategies for children can be reconsidered with special attention to their cost effectiveness.

Influenza vaccination: policy versus evidence

“…A systematic review of the incidence of influenza in people up to 19 years' old reported a seasonal variability of 0-46%; during a five year period the average incidence was 4.6% in this age group. During a period of 25 years the incidence was 9.5% in children under 5 6. Because of this variability and lack of carryover protection from one year's vaccine to the next,7 especially if the virus changes its antigenic configuration, single studies reporting data from one or two seasons are difficult to interpret.…”

What is the role of virus vaccination in patients with asthma?

“…Based on these data, the average incidence, depending on age category, is between 5% and 9.5%. The clinical picture is usually described as mild [37]. Regarding the fluctuating incidence of ILI reported, it is likely that in adults, the average incidence does not exceed these figures.…”

“…However, symptomatic disease should preferably be corroborated by a positive laboratory test [36]. Only in children do such figures seem to be available for a considerable number of years [37]. Based on these data, the average incidence, depending on age category, is between 5% and 9.5%.…”

Moeten kinderen met astma worden ingeënt tegen griep?

“…4 Een systematische review naar de incidentie van griep bij kinderen komt, bij de combinatie van door influenza veroorzaakte ziekte en bevestiging door laboratoriumonderzoek, tot een seizoensincidentie die uiteenloopt van 0 tot 48% van de populatie. 5 Als je het effect van de jaarlijkse griepvaccinatie op zijn waarde wilt beoordelen zul je echter met een gemiddelde incidentie moeten werken. Die gemiddelde incidentie per seizoen bedraagt bij kinderen van 0-5 jaar 9,5% en bij kinderen van 0-19 jaar 4,6%.…”

“…Die gemiddelde incidentie per seizoen bedraagt bij kinderen van 0-5 jaar 9,5% en bij kinderen van 0-19 jaar 4,6%. [5][6][7] Directe en indirecte complicaties van griep kunnen zijn: longontstekingen, ontregeling en ernstiger ziekte bij preëxistente aandoeningen (decompensatio cordis, diabetes mellitus, astma) en met name bij 65-plussers een verhoogde kans op overlijden. In de meeste gevallen echter is influenza bij gezonde kinderen en volwassenen een ziektebeeld dat vanzelf weer overgaat.…”