bb Rouleau 2014.

Methods	Case–control study aiming to identify what exposure factors could be linked to allergic‐like events in the general adult population
Participants	Cases of allergic‐like events were identified starting from the Quebec Adverse Events Surveillance System reviewing allergic‐like events that occurred 5 to 8 months after the vaccination campaign (between May and July 2010) and that were classified as “anaphylaxis”, ORS, or “allergy”. Cases with these diagnoses were contacted and interviewed by trained nurses who used a standardised phone questionnaire to verify the diagnosis by applying the Brighton Collaboration Criteria for Anaphylaxis and the National Advisory Committee on Immunization for ORS (bilateral red eyes, and/or facial swelling, and/or respiratory symptoms (cough, wheeze, chest tightness, difficulty breathing, difficulty swallowing/throat tightness, hoarseness or sore throat) with onset ≤ 24 hours after influenza vaccination); cases that met neither definition were considered as allergic‐like events (immediate or delayed allergic‐like events, depending on whether symptoms occurred within 4 hours after vaccination or thereafter, i.e. immediate allergic‐like events or delayed allergic‐like events). Controls were randomly selected from the Pandemic Influenza Vaccination Registry by age and sex matching of each case with 2 controls. Trained nurses collected by interview data about demographics, personal and family medical conditions, obstetric history (gravida, para, abortus), use of medication within 48 hours of vaccination, the presence of an acute respiratory illness at the time of vaccination (e.g. fever, respiratory infection, or ILI), reported allergy to potential allergenic components of the vaccine (i.e. eggs, fish, shellfish, thimerosal, latex), regular alcohol use, and physical activity. In all, 471 cases and 849 controls were identified. Of these 36 (6%) and 136 (16%) refused to participate, resulting in 435 cases (50 anaphylaxis, 177 ORS, 97 immediate allergic‐like events, and 111 delayed allergic‐like events) and 849 controls.
Interventions	A univariate analysis and multivariate logistic regression were performed with the aim of identifying potential risk (aeroallergens, drug allergy, food allergy, dermographism, hypothyroidism, family history, allergy, administration of drugs for obstructive airway disease, healthcare worker as profession, vaccinated in weeks) or protective factors (administration of anti‐inflammatory or mineral supplements, being physically active, consumption of alcohol). Separate unconditional regression models were built for each case definition and effect estimate (odds ratio) adjusted for sex and age group.
Outcomes	Exposure to vaccination with pandemic, monovalent, AS03‐adjuvanted H1N1 vaccine (Arepanrix, GSK) during the first 4 weeks of the immunisation campaign
Notes	Funding source ‐ government Exposure to vaccination is considered within the first 4 weeks of campaign (i.e. not vaccinated versus vaccinated). Among the group of vaccinated within the 4 campaign weeks, healthcare workers were strongly represented (for this group there was also significant association with all outcomes), which could have introduced a certain recall/selection bias.
Risk of bias
Bias	Authors' judgement	Support for judgement
CC ‐ case selection All outcomes	Low risk	Review of surveillance register by applying case definition during phone interview. Drawn from a nationwide active surveillance register
CC ‐ control selection All outcomes	Unclear risk	Randomly selected from a vaccination registry
CC ‐ comparability All outcomes	Low risk	Possible confounders have been considered for analysis.
CC ‐ exposure All outcomes	Unclear risk	Phone interview
Summary assessment	Unclear risk	Unclear risk of bias