Background

Influenza places a heavy public health burden in numerous countries every year. In addition to vaccines, there are some interventions that are effective in preventing influenza.

Objective

This overview of systematic reviews (SRs) aimed to evaluate the efficacy and safety of interventions for influenza prevention.

Inclusion criteria

Cochrane SRs that investigated the prevention of influenza were included. Participants included the general population without influenza or influenza-like symptoms, who were treated with preventative interventions and compared to individuals receiving no treatment or placebo.

Results

Eleven Cochrane SRs were included, covering five medications, eleven vaccinations and four complementary therapies. Among these SRs, 73% scored “high” quality on AMSTAR-II rating. We found that eight interventions, including amantadine, garlic, and six different vaccines, were beneficial for reducing the incidence of influenza compared to placebo, while oseltamivir, zanamivir, Ganmao capsule, Echinacea, and another three types of vaccine were probably beneficial. Ganmao capsule ranked highest for influenza prevention in the network meta-analysis, followed by amantadine, garlic, and vaccines of all types. Monovalent inactivated parenteral vaccine was found to be beneficial in reducing the incidence of influenza-like illness. None of the interventions reduced the hospitalization rate.

Conclusions

High-quality evidence showed that garlic or vaccine had advantages in preventing influenza, and that vitamin C is not effective. The effect of other interventions needs to be further verified with high-quality evidence.

Key words: Influenza, Preventive measure, Overview, Network meta-analysis, Evidence mapping, Systematic review