pba Benowitz 2010.

Methods	Case‐control study assessing the effectiveness of influenza vaccination of pregnant women in preventing hospitalisation for influenza in their newborns. Study period ranged from October 2000 to April 2009.
Participants	Cases (n = 113): infants below 12 months hospitalised for influenza between October 2000 and April 2009 who tested positive for influenza with direct fluorescent antibody (DFA) Controls (n = 192): participants hospitalised for influenza during the same time interval as the cases but negative with the DFA test. For each case 1 or 2 controls matched for birth date and date of hospitalisation were randomly selected.
Interventions	Immunisation with influenza vaccine during pregnancy (until 14 days before delivery)
Outcomes	DFA‐confirmed influenza
Notes	This study was supported by the National Center for Research Resources, a component of the National Institutes of Health.
Risk of bias
Bias	Authors' judgement	Support for judgement
CC ‐ case selection All outcomes	Low risk	Infants hospitalised with DFA positive
CC ‐ control selection All outcomes	Low risk	Infant hospitalised with DFA negative
CC ‐ comparability All outcomes	Low risk	Matching
CC ‐ exposure All outcomes	Unclear risk	Structured interview
Summary assessment	Unclear risk	Unclear