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Introduction—flu vaccines in children and indirect effects
Influenza is an important cause of morbidity and mortality, especially in combination with secondary bacterial infections.1–3 Annual influenza vaccination is recommended for everyone at risk by the WHO.4 In recent years, a number of countries have recommended influenza vaccination for all children older than 6 months although the uptake has been variable. The effectiveness of inactivated influenza vaccines in children has been questioned.5 Numerous studies have been published on the subject but outcome measures used vary with some studies using influenza-like-illness while others use culture or PCR-proven influenza, making comparison and meta-analyses difficult. In several randomised clinical trials, live attenuated influenza vaccine (LAIV) has been found safe, effective compared to placebo and consistently more effective than trivalent inactivated vaccine (TIV) in children. In 2012, UK authorities announced plans to offer annual LAIV to all children aged 2–17 years and in July 2013 that a single dose of the vaccine will be offered to all 2-year-olds and 3-year-olds from September 2013. Although the evidence base supporting this decision is robust, some important questions remain unanswered. Such a campaign, if carried out successfully, could significantly reduce the burden of disease in children and, since children are thought to be important in the propagation of infection within the population and thus development of influenza epidemics, this initiative may well impact on disease in other age groups through indirect protection. However, few studies quantifying such effects have been done to date. In this paper, aspects of the implementation of universal childhood influenza vaccination are discussed.
Disease burden, epidemiology and interactions with bacteria
Although it is widely believed to be a relatively insignificant infection in childhood, between 10% and 30% of children are infected with influenza during every annual epidemic,6–8 an attack rate higher than any other age group with a rate of complications that is especially high in the …