Abstract
Since the mid-1980s, two lineages of influenza B viruses have been distinguished. These can co-circulate, limiting the protection provided by inactivated trivalent influenza vaccines (TIVs). This has prompted efforts to formulate quadrivalent influenza vaccines (QIVs), to enhance protection against circulating influenza B viruses. This review describes the results obtained from seven phase III clinical trials evaluating the immunogenicity, safety, and lot-to-lot consistency of a new quadrivalent split-virion influenza vaccine (Vaxigrip Tetra®) formulated by adding a second B strain to the already licensed TIV. Since Vaxigrip Tetra was developed by means of a manufacturing process strictly related to that used for TIV, the data on the safety profile of TIV are considered supportive of that of Vaxigrip Tetra. The safety and immunogenicity of Vaxigrip Tetra were similar to those of the corresponding licensed TIV. Moreover, the new vaccine elicits a superior immune response towards the additional strain, without affecting immunogenicity towards the other three strains. Vaxigrip Tetra is well tolerated, has aroused no safety concerns, and is recommended for the active immunization of individuals aged ≥6 months. In addition, preliminary data confirm its immunogenicity and safety even in children aged 6–35 months and its immunogenicity in older subjects (aged 66–80 years).
Highlights
Influenza is an acute viral respiratory disease caused by RNA-enveloped viruses which belong to the family of Orthomyxoviridae and are transmitted principally through aerosols and droplets generated by coughing and sneezing by infected people
Similar solicited reactions, unsolicited adverse events (AEs), and serious adverse events (SAEs) were reported in the quadrivalent influenza vaccines (QIVs) and pooled trivalent influenza vaccines (TIVs) groups
The current virological situation and the difficulty in predicting which influenza B virus lineage will be prevalent during the influenza season have reduced immunological protection among vaccinated individuals
Summary
Influenza is an acute viral respiratory disease caused by RNA-enveloped viruses which belong to the family of Orthomyxoviridae and are transmitted principally through aerosols and droplets generated by coughing and sneezing by infected people. When circulating influenza B and B vaccine strains match, drops dramatically (46–49%) in the case of mismatch, significantly limiting the protective effects of TIVs [34], mainly in high-risk groups, such as the elderly, as reported by the group of De Jong [35] during the major epidemic A(H3N2) virus strain. These data underscore the need to broaden protection by using quadrivalent influenza vaccines (QIVs) [25], as was proposed by the US FDA in 2007 [36]. 2013–14 and 2015–16 seasons [40]
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