July 15, 2020

Comparativeness effectiveness of influenza vaccines in elderly persons

Q# 19-07 – Comparativeness effectiveness of influenza vaccines in elderly persons

Research question:

Which influenza vaccine available for adults 65 years of age and older is the most effective?


Influenza respiratory infections are caused primarily by influenza A and B viruses with worldwide annual attack rate estimated at 5–10% in adults. Influenza is recognized as a cause of a broad spectrum of morbidity and mortality. In Canada, it is estimated 12,200 hospitalizations and 3,500 deaths attributable to influenza annually [1].

Vaccination is the most effective way to prevent influenza and its complications. In Canada, there are currently four types of influenza vaccines available for adults 65 years of age and older, the target population of the present project: trivalent standard dose (Agriflu®, Fluviral®, Influvac®), quadrivalent standard dose (Afluria® Tetra, Influvac® Tetra, Flulaval Tetra®, Fluzone® Quadrivalent), trivalent adjuvanted (Fluad®), and trivalent high dose (Fluzone® High-Dose). The National Advisory Committee on Immunization (NACI) informs that there are insufficient head-to-head studies directly comparing efficacy, effectiveness, and immunogenicity of trivalent adjuvanted, trivalent high dose, and quadrivalent standard dose [1]. Further investigations are required to provide real-world evidence on comparative effectiveness of influenza vaccine in seniors.

CAN-AIM proposes a retrospective cohort study to compare the effectiveness of the above four types of influenza vaccine in adults 65 years of age and older using administrative databases from the United States.

Current status:

The PMAP for the current study was approved in December 2019. The analytical protocol has been developed and was sent to DSEN. In the study we will use six cohorts based on MarketScan® databases (2012-2018). We have constructed our first cohort covering the 2017/2018 influenza season. After applying the inclusion and exclusion criteria, we have included 218,592 adults 65 years of age and older that had received influenza vaccination during this period (53.3% trivalent high dose, 31.0% quadrivalent standard dose, 11.4% trivalent standard dose, and 4.3% trivalent adjuvanted). In the next months we will proceed cohort selection for the other periods and start the analysis of all six cohorts.