Fig. 3From: Frequency and impact of confounding by indication and healthy vaccinee bias in observational studies assessing influenza vaccine effectiveness: a systematic reviewOdds ratios (95 % CIs) of influenza vaccine effectiveness during influenza seasons (black square), during pre-influenza seasons (striped circle) and post-influenza seasons (white circle) against all-cause mortality (a), death due to respiratory event (b), death due to cardiac event (c), and major adverse vascular event (d)Back to article page