pba Poehling 2011.

Methods	Case‐control study assessing the effectiveness of influenza vaccine administered during pregnancy in preventing influenza in newborns under 6 months
Participants	Children (n = 1510) aged below 6 months who were hospitalised for fever or acute respiratory illness, or both during 7 consecutive epidemic seasons (between 2002 and 2003 and 2008 and 2009). Those with positive laboratory confirmation of influenza were enrolled as cases (n = 151); those whose result was negative were enrolled as controls (n = 1359).
Interventions	Influenza vaccination during pregnancy
Outcomes	Influenza
Notes	This project was supported the Centers for Disease Control and Prevention, National Institute of Allergy and Infectious Diseases, and Wachovia Research Fund. 3 authors had received past funding from industry (of these 1 was on the MedImmune Advisory Board and another was a NexBio consultant). Funding source ‐ mixed
Risk of bias
Bias	Authors' judgement	Support for judgement
CC ‐ case selection All outcomes	Low risk	Laboratory confirmed
CC ‐ control selection All outcomes	Low risk	Infants without laboratory‐confirmed influenza
CC ‐ comparability All outcomes	Unclear risk	No matching, unclear information
CC ‐ exposure All outcomes	Unclear risk	Structured interview
Summary assessment	Unclear risk	Unclear