Skip to main content

Table 3 Incident rate ratios, with 95% confidence intervals (CIs) for cardiovascular events following pandemic influenza vaccination (pandemrix) among lower risk individuals

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

  AMI (n = 495) Stroke (n = 308) Pulmonary embolism (n = 136)
No. of events Person-days at risk IRR (95% CI)b No. of events Person-days at risk IRR (95% CI)b No. of events Person-days at risk IRR (95% CI)b
Baseline perioda 209 160,056 1.00 (ref.) 160 99,468 1.00 (ref.) 59 44,064 1.00 (ref)
Pre-vaccination interval          
 1–14 days 2 6916 0.29 (0.07–1.19) 4 4298 0.63 (0.23–1.74) 1 1904 0.59 (0.08–4.50)
 On the day of vaccination No estimates No estimates No estimates
Post-vaccination interval          
 1–14 days 29 6916 4.19 (2.69–6.52) 11 4298 1.73 (0.90–3.31) 4 1904 2.35 (0.78–7.06)
 15–28 days 24 6916 3.17 (1.99–5.07) 10 4298 1.51 (0.77–2.97) 5 1904 2.61 (0.96–7.08)
 29–59 days 43 15,314 2.28 (1.50–3.49) 22 9517 1.40 (0.81–2.42) 7 4216 1.40 (0.56–3.52)
 60–90 days 57 15,314 2.78 (1.79–4.32) 31 9517 1.86 (1.04–3.32) 20 4216 3.43 (1.57–7.47)
 91–120 days 46 14,820 2.27 (1.50–3.44) 22 9210 1.37 (0.76–2.46) 18 4080 3.10 (1.50–6.41)
 121–180 days 85 29,640 1.99 (1.54–2.59) 48 18,420 1.54 (1.10–2.17) 22 8160 1.80 (1.08–3.00)
  1. These are results from self-controlled case series analysis using data for first-time AMI (n = 495), stroke (n = 308) and pulmonary embolism (n = 136) 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)
  2. AMI acute myocardial infarction, IRR incident rate ratio, CI confidence interva
  3. aAll remaining part of the observation period was used for baseline comparison (unexposed person-time)
  4. bAdjusted for calendar period (January-March, April-August, and September-December)