The effectiveness and efficacy of influenza vaccines among children: a systematic review of RCTs (2011-2019)

Abstract

Background Seasonal influenza viruses evolve continuously, which means that people can become infected multiple times throughout their lives. Thus, in order to reduce the incidence of influenza and its complications, vaccination is recommended as the most effective preventative strategy, but this strategy is challenging because the disease is caused by different strains of the virus in each season. The influenza vaccination is recommended for children from ≥ 6 months to 18 years old, adults aged 65 years old and over, people with chronic medical conditions, pregnant women and healthcare workers.

Aim and design To assess the highest quality evidence about the effectiveness and efficacy of licensed influenza vaccines in children aged 6 months to 18 years, a systematic review of randomised controlled trials (RCTs) was conducted.

Data processing and analysis Searches yielded 5160 results; 9 articles were included in the review. Information from these articles was extracted and a standardised tool was used for appraisal.

Results Each of the nine articles assessing the efficacy in terms of reducing the numbers of laboratory-confirmed influenza. Only two studies assessed the effectiveness in terms of reducing the incidence of influenza-like illness. Harvest plots were used to illustrate the characteristics of included studies and the weight of evidence regarding the efficacy and effectiveness of live-attenuated and inactivated vaccines. Both vaccine types showed high efficacy and effectiveness based on evidence from the literature included in this review. In addition, both live and inactivated vaccines were more efficacious against infection with influenza virus strains that were similar antigenically to strains contained in the vaccine.

Conclusion Despite of some limitation in the review (e.g. only studied from 2011 onwards were included and some studies showed some concerns regarding deviations from intended interventions and in measurement of the outcome domains), this systematic review shows clearly, via evidence from clinical trials, that the influenza vaccination remains the best way compare to others interventions to protect against influenza, given that it is effective and that it probably assists children against influenza infection, respiratory illness and other influenza-related complications.