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Table 4 Incident rate ratios, with 95% confidence intervals (CIs) for cardiovascular events following pandemic influenza vaccination (pandemrix) among higher risk individuals, stratified by antiplatelet users versus non-users

From: Influenza vaccination and risk for cardiovascular events: a nationwide self-controlled case series study

   AMIa   Strokea   Pulmonary embolisma
Anti-platelet users (n = 3932)   Antiplatelet non-users (n = 1097) Anti-platelet users (n = 2203)   Antiplatelet non users (n = 923) Anti-platelet users (n = 319)   Antiplatelet non users (n = 540)
N IRR (95% CI)c N IRR (95% CI)c N IRR (95% CI)c N IRR (95% CI)c N IRR (95% CI)c N IRR (95% CI)c
Baseline periodb 2921 1.0 (ref.) 443 1.0 (ref.) 1561 1.00 (ref.) 500 1.0 (ref.) 194 1.00 (ref.) 370 1.0 (ref)
Pre vaccination interval             
 1–14 days 117 0.87 (0.71–1.06) 8 0.51 (0.25–1.05) 45 0.69 (0.51–0.94) 10 0.51 (0.27–0.98) 7 0.92 (0.42–2.01) 23 1.37 (0.88–2.14)
Post vaccination interval             
 1–14 days 55 0.41 (0.31–0.54) 50 3.28 (2.37–4.54) 39 0.60 (0.43–0.84) 25 1.29 (0.84–1.97) 10 1.30 (0.66–2.56) 8 0.48 (0.23–0.98)
 15–28 days 64 0.48 (0.37–0.62) 37 2.35 (1.64–3.38) 45 0.70 (0.52–0.96) 35 1.78 (1.24–2.57) 6 0.76 (0.33–1.77) 16 0.96 (0.57–1.61)
 29–59 days 167 0.58 (0.49–0.68) 111 3.15 (2.46–4.03) 114 0.84 (0.68–1.03) 67 1.50 (1.12–2.01) 23 1.19 (0.72–1.98) 26 0.71 (0.45–1.10)
 60–90 days 160 0.59 (0.47–0.75) 101 2.77 (2.08–3.70) 94 0.74 (0.56–0.99) 76 1.62 (1.15–2.29) 20 0.86 (0.45–1.64) 19 0.52 (0.29–0.95)
 91–120 days 169 0.65 (0.52–0.82) 124 3.34 (2.55–4.36) 98 0.79 (0.60–1.05) 70 1.53 (1.09–2.16) 25 1.10 (0.59–2.04) 24 0.69 (0.40–1.19)
 121–180 days 279 0.53 (0.46–0.61) 220 2.64 (2.22–3.13) 207 0.74 (0.64–0.87) 140 1.48 (1.21–1.81) 34 0.85 (0.56–1.28) 54 0.79 (0.58–1.09)
  1. AMI acute myocardial infarction, IRR incident rate ratio, CI confidence interval
  2. aAnalyses was restricted among higher cardiovascular-risk patients. These are results from self-controlled case series analysis using data for first-time AMI, stroke and pulmonary embolism patients who were vaccinated with Pandemrix. The start of observation period was May 1, 2009 and end of observation period was September 30, 2010 or the day of emigration or death (whichever came first). Person-time of each vaccinated individual was divided into following risk-periods: pre-vaccination interval (1–14 days prior to vaccination) and postvaccination intervals (1–14 days, 15–28 days, 29–59 days, 60–90 days, 91–120 days, 121–180 days following vaccination)
  3. bAll remaining part of the observation period was used for baseline comparison (unexposed person-time)
  4. cAdjusted for calendar period (January–March, April–August, and September–December)