Table 4

Summary table of case–control studies of the association between influenza vaccination and AMI

Paper, yearStudy locationStudy designParticipant age
Mean (range)*
Prior AMI in study participantsVaccination of cases
n/N (%)
Vaccination of controls
n/N (%)
OR (95% CI)Adjusted confoundersaOR (95% CI)Risk of bias score
Meyers39Kansas City, USAHospital-based retrospective study with patient follow-upCases: 66±11
Controls: 74±11
Exclusion criteria not reported177/335 (52.8)126/199 (63.3)0.65 (0.45 to 0.93)Gender, age, BMI, ever smoked, positive family history, previous heart disease, number of URTI, URTI within 2 weeks before AMI0.92 (0.60 to 1.42)Moderate
Heffelfinger et al40Seattle, USARetrospective HMO database studyCases: 72.9
Controls: 73.7
Cases: Prior MI excluded
Controls: males hypertensive
494/750 (65.8)1145/1735 (66.0)0.99 (0.83 to 1.19)†Age, gender, history of treated hypertension, index year, pre-existing cardiovascular disease, presence of treated hyperlipidaemia, DM, current smoking and COPD/asthma0.98 (0.75 to 1.30)Moderate
Macintyre et al27Sydney, AustraliaProspective hospital-based studyAged ≥40 yearsCases: prior AMI eligible (NNR)
Controls: 12-month history of AMI, TIA or stroke excluded
92/275 (33.5)184/284 (64.8)0.27 (0.19 to 0.39)†Age, gender, smoking, high cholesterol0.55 (0.35 to 0.85)Low
Naghavi et al36Houston, USAProspective study based in cardiology outpatient department in a university hospitalCases: 62.9±11.9
Controls: 64.6±13.5
All with prior history of MI
50/109 (45.8)73/109 (67.0)0.42 (0.24 to 0.72)†Current smoking, current hypertension, current hypercholesterolaemia, multivitamin, physical activity (20–30 min 3–4 times/week), history of influenza vaccine in previous years, age ≥60 years0.33 (0.13 to 0.82)Moderate
Puig-Barbera et al37Valencia Autonomous Region, SpainProspective hospital-based study in three health districtsCases: 75.7 (6.8)
Controls: 78.8 (7.6)
Prior MI not an exclusion criteria (NNR)114/144 (79.2)181/258 (70.2)1.61 (1.0 to 2.62)†Propensity score, at least 3 cardiovascular risk factors0.13 (0.03 to 0.65)Moderate
Siriwardena et al38UKRetrospective study of representative GP databaseAged ≥40 yearsCases: prior MI excluded
Controls: exclusion not reported
8472/16 012 (52.9)32 081/62 694 (51.2)1.07 (1.04 to 1.11)†Age, gender, smoking, DM, hypertension, previous cardiovascular disease, hyperlipidaemia, family history of AMI0.81 (0.77 to 0.85)Moderate
Warren-Gash et al28London, EnglandProspective hospital-based study; 2009–2010 influenza seasonAged ≥40 years
63.6 (IQR 53.3–72.6)
Cases: prior AMI eligible (14/70)
Controls: 1-month history of AMI excluded (5/64 prior AMI)
30/70 (42.9)29/64 (45.3)0.91 (0.46 to 1.79)†Age, gender, month of admission and history of AMI0.46 (95% CI 0.19 to 1.12) Low
  • *Unless otherwise reported. †Calculated from included data (not reported in original paper).

  • AMI, acute myocardial infarction; BMI, body mass index; COPD, chronic obstructive pulmonary disease; DM, diabetes mellitus; HMO, health maintenance organisation; IQR, interquartile range; MI, myocardial infarction; NNR, number not reported; URTI, upper respiratory tract infection; TIA, transient ischaemic attack.