Annual influenza vaccinations are widely recommended, yet recent observational studies have suggested that vaccination across consecutive years may contribute to reduced vaccine effectiveness.
To address this hypothesis, IIDR trainee Jessica Bartoszko of Dr. Mark Loeb’s lab synthesized evidence from 5 randomized controlled trials and 28 observational studies reporting influenza infections over 2 or more consecutive influenza seasons.
The study found that available evidence does not support a reduction in the effectiveness of influenza vaccines when persons vaccinated in two consecutive seasons (current and prior season) were compared to persons vaccinated in the current season alone. However, these findings do not completely rule out the possibility of reduced effectiveness.
Read the full publication here.