Vaccine Efficacy & Effectiveness

The efficacy and effectiveness of different split virion and subunit influenza vaccines are generally considered equivalent. 

The efficacy and effectiveness of influenza vaccine depends primarily on the age and immunocompetence of the vaccine recipient, and the degree of similarity between the virus strains in the vaccine and those circulating in the community.

During a season with good vaccine match, vaccine effectiveness was between 60 and 85% in children ranging in age from 6 months to <6 years.

A recent systematic review estimated the overall efficacy of inactivated vaccines against laboratory-confirmed influenza in healthy adults <65 years of age to be 59%, although efficacy varied by influenza season.

The efficacy of inactivated influenza vaccine against influenza-like illness in persons ≥65 years of age living in the community is estimated to be 43% when viral circulation is high, although there have been few randomised controlled trials of influenza vaccine in elderly people.

A systematic review assessing vaccine effectiveness estimated that during periods of high virus circulation, when vaccine match is good, influenza vaccination is approximately 45% effective against hospitalisations due to influenza and pneumonia and 60% effective against all-cause mortality in persons aged >65 years in nursing home settings.1

Currently available influenza vaccines confer protection for about a year. Low levels of protection may persist for a further year, if the prevalent strain remains the same or undergoes only minor antigenic drift. Continuing protection requires annual vaccination with vaccine containing the most recent strains.1



1. NHMRC. The Australian Immunisation Handbook 10th Edition 2015. Available here

Last updated:  20 April 2016