OBJECTIVES

To assess resource clinical impact and consumption savings associated to influenza vaccination of the Portuguese elderly population with a high dose quadrivalent influenza vaccine (HD-QIV) vs. a standard dose quadrivalent influenza vaccine (SD-QIV).

METHODS

A decision tree model, with a one-year time horizon, was used to compare the disease burden of influenza in adults aged 65 years or older vaccinated with HD-QIV vs. SD-QIV. The decision tree allows to predict influenza cases, influenza-related general practitioner (GP) visits, emergency room (ER) visits, hospitalizations, influenza-related deaths.

The attack rate of influenza associated to each vaccination strategy is based on that of an unvaccinated cohort, the coverage rate, and the efficacy of each vaccine. The probability of an ER or GP visit conditional on developing influenza was based on Portuguese data.

Two definitions were used for hospitalization data: influenza related hospitalizations and cardiorespiratory hospitalizations (possibly attributable to influenza). All demographic, epidemiological, and economic inputs were based on Portuguese data. Relative efficacy of HD-QIV vs. SD-QIV was assumed to be like the 24,5% relative efficacy of high dose trivalent influenza vaccine vs. standard dose trivalent influenza vaccine observed in FIM12 randomized clinical trial.

RESULTS

In Portugal, switching from SD-QIV to HD-QIV in adults over 65 years, assuming a coverage rate of 65%, would allow a reduction of 13,461 influenza cases (12%), with 378 fewer deaths (12%). It also allows a reduction of 1,229 GP appointments and 532 ER visits. Concerning hospitalizations, influenza-related ones are reduced by 121 (10%), while those related to respiratory and cardiorespiratory complications are decreased by 5,112 (14%) and 8,755 (11%), respectively.

CONCLUSIONS

A switch to HD-QIV seasonal vaccination in the elderly Portuguese population would contribute to reach public health objectives, reducing excess mortality and the consumption of healthcare resources.