Seasonal influenza is an infectious respiratory disease which circulates annually and is associated with a considerable health and economic burden globally. The most effective means of preventing seasonal influenza is through strain-specific vaccination. 

For many decades, only trivalent influenza vaccines (that include two influenza A strains and one influenza B strain) were available. In recent years, quadrivalent (two influenza A strains and two influenza B strains) vaccines have been authorised and are increasingly available. The 2020/2021 HSE seasonal vaccination programme offers the quadrivalent influenza vaccine. 

Vaccine manufacturers have developed variations on traditional influenza vaccines (collectively termed newer and enhanced vaccines) in an attempt to improve vaccine effectiveness. These vaccines are typically marketed at an increased cost. Decision-making groups in Europe and beyond require a systematic and independent assessment of the safety and effectiveness of these products to inform public health strategies and reimbursement decisions. 

The objective of this systematic review is to assess and synthesise the literature on the efficacy, effectiveness and safety of newer and enhanced inactivated seasonal influenza vaccines for the prevention of laboratory-confirmed influenza in individuals aged 18 years or older, namely: MF59® adjuvanted, cell-based, high-dose, and recombinant haemagglutinin (HA) influenza vaccines.

This systematic review was conducted under contract between the European Centre for Disease Prevention and Control (ECDC) and HIQA. The work was undertaken by HIQA in collaboration with the ECDC and a Working Group under the EU/EEA National Immunisation Technical Advisory Group Collaboration.