pca Munoz 2005.

Methods	Retrospective cohort study based on the electronic database of Kelsey‐Seybold Clinic (KSC), a large multispecialty clinic in the metropolitan area of Houston (USA). For the study 5 subsequent flu seasons were considered, from 1998 to 2003, taking into account the time between 1 July and 30 June of each year. Approximately 25 obstetricians and 60 paediatricians provided medical care in KSC locations, and about 2500 deliveries occurred every year during the time considered for the study.
Participants	Exposed cohort (n = 225): women who were immunised with inactivated influenza vaccine within 6 months before delivery and who had an uncomplicated singleton pregnancy, were healthy, had at least 1 prenatal care visit at KSC, and their offspring had at least 1 clinic visit at KSC in their first year of life. Comparison (n = 826): for each vaccinated woman, a comparison group was selected by matching (KSC database) 3 to 5 women for maternal age at delivery, month of delivery, and type of insurance (with the exclusion of both Medicaid or self insurance due to small numbers in this clinic population), who had not received influenza vaccine during pregnancy.
Interventions	Influenza vaccines used during the study period were Aventis Pasteur or Wyeth products. For the control group the index date ("pseudo vaccination date") corresponds to the same number of days before delivery as the real vaccination date for a matching vaccinated woman.
Outcomes	Women Acute respiratory illness: cases recorded at any time, during each flu season and during each epidemic peak of that season diagnosed with the following ICD‐9 codes: 079, 460‐466, 470‐478, 480‐487. The peak of influenza activity was the period during which the number of laboratory‐confirmed cases included at least 85% of influenza cases for that season. Serious adverse events: hospitalisation (death, cause for hospitalisation, and permanently disabling conditions were also included) within 42 days from immunisation identified by ICD‐9 codes. Medical diagnoses occurred between vaccination and delivery with an incidence ≥ 2% among vaccinated women. Newborns Diagnoses different from a “normal newborn infant” given at discharge and within 2 days from delivery. Reason for at least 3 days hospitalisation within 1 week, between 8 and 180 days, and between 6 months and 1 year after delivery. Diagnoses reported during ambulatory medical visits during the first 6 months of life. In the last 2 categories URTI and respiratory infections are also included.
Notes	Little information about characteristics and comparability of the exposed and unexposed cohorts. Outcomes used to assess the effectiveness of vaccination are in some way 'surrogate' and include only hospitalisation and ambulatory diagnoses. The first 2 weeks after vaccination should have been excluded from follow‐up for the assessment of effectiveness in mothers. Government funded
Risk of bias
Bias	Authors' judgement	Support for judgement
PCS/RCS ‐ selection exposed cohort All outcomes	Unclear risk	Women were included in the study sample if they had received inactivated influenza vaccine within 6 months before delivery of an uncomplicated singleton pregnancy and were otherwise healthy, had at least 1 prenatal care visit at KSC, and their offspring had at least 1 clinic visit at KSC in their first year of life.
PCS/RCS ‐ selection non‐exposed cohort All outcomes	Unclear risk	A comparison group was selected by matching of maternal age at delivery, month of delivery, and type of insurance (patients with Medicaid or self insurance were excluded due to the small numbers in this clinic population). For each vaccinated woman, 3 to 5 (ratio 1:3.5) matching healthy women who met all the inclusion criteria but who had not received influenza vaccine during pregnancy were selected.
PCS/RCS ‐ comparability All outcomes	Unclear risk	Matching
PCS/RCS ‐ assessment of outcome All outcomes	Unclear risk	The potential protective effect of the vaccine was estimated by recording the occurrence of ARIs in vaccinated women from the time of receipt of influenza vaccine to delivery and in unvaccinated women for the equivalent period of time. Specifically, the occurrence of ARIs during the peak of the influenza season was compared between the groups. Diagnostic codes for ARI included 079, 460‐466, 470‐478, 480‐487.
Summary assessment	Unclear risk	Unclear