Trivalent
influenza vaccines encompass one influenza B lineage; however,
predictions have been unreliable on which of two antigenically distinct
circulating lineages will dominate. Quadrivalent seasonal influenza
vaccines contain strains from both lineages. This analysis assesses the
cost effectiveness of switching from trivalent inactivated influenza
vaccination (TIV) in Finland to quadrivalent vaccination, using
inactivated (QIV) or live-attenuated (Q-LAIV) vaccines.

A
transmission model simulated the dynamics of influenza infection while
accounting for indirect (herd) protection. Prior distributions for key
transmission parameters were repeatedly sampled and simulations that
fitted the available information on influenza in Finland were recorded.
The resulting posterior parameter distributions were used in a
probabilistic sensitivity analysis in which economic parameters were
sampled, simultaneously encompassing uncertainty in the transmission and
economic parameters. The cost effectiveness of a range of trivalent and
quadrivalent vaccine policies over a 20-year time horizon was assessed
from both a societal and payer perspective in 2014 Euros.

The
simulated temporal incidence pattern of symptomatic infections
corresponded well with case surveillance data. A switch from the current
TIV to Q-LAIV in children (2 to <18 years) and to QIV in other ages
was estimated to annually avert approximately 76,100 symptomatic
infections (95 % range 36,700–146,700), 11,500 primary care
consultations (6100–20,000), 540 hospitalisations (240–1180), and 72
deaths (32–160), and was cost-saving relative to TIV (€374 million
averted [€161–€752], in 2014 Euros, discounted at 3 %). This scenario
had the highest probability of being the most cost-effective scenario
considered.

This
analysis demonstrates that quadrivalent vaccination is expected to be
highly cost effective, reducing the burden of influenza-related disease.