The interplay between population susceptibility and vaccine effectiveness control the timing and size of an emerging influenza wave #

Edwin Van Leeuwen

11:30 Monday in 2Q50/51.

Part of the How to be better prepared for a future pandemic: lessons learned from COVID-19, mpox and the four historic influenza pandemics session.

Abstract #

Relaxing social distancing measures and reduced level of influenza over the COVID-19 seasons has led to a winter 2022 influenza wave in England over the period October to December 2022. We used an established model for influenza transmission and vaccination to evaluate the rolled out influenza immunisation programme over October to December 2022. Specifically, we explored how the interplay between pre-season population susceptibility and influenza vaccine efficacy control the timing and the size of a possible winter influenza wave. Our findings suggest that susceptibility affects the timing and the height of a potential influenza wave, with higher susceptibility leading to an earlier and larger influenza wave while vaccine efficacy controls the size of the peak of the influenza wave. With pre-season susceptibility higher than pre-COVID-19 levels, under the planned vaccine programme an early influenza epidemic wave is possible, its size dependent on vaccine effectiveness against the circulating strain. If pre-season susceptibility is low and similar to pre-COVID levels, the planned influenza vaccine programme with an effective vaccine could largely suppress a winter 2022 influenza outbreak in England. By simulating different combinations of population susceptibility and vaccine effectiveness, we also characterise the experienced influenza wave over the period October-December 2022 with these two parameters.