Figure 1.

Evaluation of the modifying effect of vaccination history on the effect of influenza vaccination in the current season for all patients and by healthcare setting, Navarre, Spain, pooled analysis of the 2011/12–2018/19 influenza seasons (n = 10,356)

^a Influenza vaccination effect and 95% confidence interval (in brackets), adjusted by age groups (9–44, 45–64, 65–84 and ≥ 85 years), major chronic conditions, healthcare setting (primary healthcare and hospital) and month and season of sample collection.

^b p value < 0.05 for comparison with the category of current season vaccination and no prior doses.