Vaccine efficacy and effectiveness

Measuring the efficacy and effectiveness of inactivated influenza vaccine and forming generalizable conclusions about it is challenging because of both the difficulty of identifying the burden of influenza disease and the difficulty of matching the vaccine to the circulating strains which may vary each year.


The WHO field guide for evaluation of influenza vaccine effectiveness supports the generation of reliable national data on the impact of influenza vaccine and provides advice on the design of observational influenza vaccine effectiveness studies.

Reports from two recent randomized controlled clinical studies in South Africa (2013) and Bangladesh (2014) [3, 14] indicated an efficacy in the range of 35–70% in pregnant women and 28–61% in infants less than 6 months old when tested against laboratory-confirmed influenza disease.