Table 1.

Inclusion and exclusion criteria for literature search

Study inclusion criteria	Study exclusion criteria
Referring to seasonal influenza vaccination	No reference to seasonal influenza vaccination
Focusing on factors or determinants of	No inclusion of determinants or
influenza vaccine hesitancy	factors of influenza vaccine hesitancy
Focusing on pregnant women	No focus on pregnant women
Focusing on European countries	No focus on countries in WHO European region
Published in English	Published in languages other than English
Published between 01.01.2009 and 11.30.2019	Published before or after 01.01.2009 and 11.30.2019
Primary studies	Secondary studies (meta-analysis or systematic
Peer-reviewed journal articles	Gray literature
Humans	Focusing on vaccine uptake rather than hesitancy