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How well does a flu vaccine work? DRIVE evaluates performance

Despite challenging conditions posed by the COVID-19 outbreak, the DRIVE project successfully tested how well various brands of flu vaccines worked across five European countries and a range of age groups, and published their results in the scientific journal Frontiers Public Health.

08 January 2024
A doctor administering a vaccine to a patient. Image credit: Prostock Studio via Shutterstock
A doctor administering a vaccine to a patient. Image credit: Prostock Studio via Shutterstock

Between four and 50 million European citizens snuffle through flu each year, and sadly between 15 000 and 70 000 people die either due to the virus itself or complications arising from its onset. Several different brands of influenza vaccine are available in Europe any given year – however the performance of these vaccines varies.

The discrepancies in performance could be related to the strain of virus that is circulating as well as other factors such as the technology used to manufacture the vaccine, the age of the recipients of the vaccine or whether recipients were resident in a hospital or primary care setting versus living at home. Knowing what works best, and under which circumstances, could improve outcomes and lead to better protection against influenza, and so in 2017 the European Medicines Agency called on vaccine manufacturers to start tracking the performance of their vaccines. As a result the DRIVE project was set up under the framework of IMI to develop a system that could be used to evaluate brand-specific flu vaccine effectiveness.

Eight different influenza vaccines were studied by the DRIVE project across five European countries from 2018 to 2022. The project came up with several brand-specific influenza vaccine effectiveness estimations across different influenza strains, patient age groups and whether the patients were resident in hospital settings or primary care centres versus living at home.

However the results must be interpreted with caution – a small sample size resulted in large confidence intervals (although 35 000 people were involved in DRIVE’s study) as thanks to COVID-19 there was limited circulation of influenza virus in Europe during the study years.

Sensitivity tests were also performed to exclude confounding variables, and observed differences between populations were noted – for example, excluding subjects with more than four days’ time recorded between the onset of their illness and the taking of a swab decreased observed vaccine effectiveness in children and younger adults but not in older adults.

The project has ended, however discussions are ongoing with the European Medicines Agency to improve the monitoring of vaccine effectiveness in Europe.

DRIVE was supported by the Innovative Medicines Initiative, a partnership between the European Union and the European pharmaceutical industry.