title: Risk of myocardial infarction and stroke after acute infection or vaccination.
abstract: BACKGROUND
  There is evidence that chronic inflammation may promote atherosclerotic disease. We tested the hypothesis that acute infection and vaccination increase the short-term risk of vascular events.
  
  
  METHODS
  We undertook within-person comparisons, using the case-series method, to study the risks of myocardial infarction and stroke after common vaccinations and naturally occurring infections. The study was based on the United Kingdom General Practice Research Database, which contains computerized medical records of more than 5 million patients.
  
  
  RESULTS
  A total of 20,486 persons with a first myocardial infarction and 19,063 persons with a first stroke who received influenza vaccine were included in the analysis. There was no increase in the risk of myocardial infarction or stroke in the period after influenza, tetanus, or pneumococcal vaccination. However, the risks of both events were substantially higher after a diagnosis of systemic respiratory tract infection and were highest during the first three days (incidence ratio for myocardial infarction, 4.95; 95 percent confidence interval, 4.43 to 5.53; incidence ratio for stroke, 3.19; 95 percent confidence interval, 2.81 to 3.62). The risks then gradually fell during the following weeks. The risks were raised significantly but to a lesser degree after a diagnosis of urinary tract infection. The findings for recurrent myocardial infarctions and stroke were similar to those for first events.
  
  
  CONCLUSIONS
  Our findings provide support for the concept that acute infections are associated with a transient increase in the risk of vascular events. By contrast, influenza, tetanus, and pneumococcal vaccinations do not produce a detectable increase in the risk of vascular events.
authors.affiliation: Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom. liam.smeeth@lshtm.ac.uk
authors.forename: Liam
authors.initials: L
authors.lastname: Smeeth
authors.forename: Sara L
authors.initials: SL
authors.lastname: Thomas
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Hall
authors.forename: Richard
authors.initials: R
authors.lastname: Hubbard
authors.forename: Paddy
authors.initials: P
authors.lastname: Farrington
authors.forename: Patrick
authors.initials: P
authors.lastname: Vallance
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016208:Databases, Factual; D006801:Humans; D015994:Incidence; D007252:Influenza Vaccines / Q000009:adverse effects; D008875:Middle Aged; D009203:Myocardial Infarction / Q000209:etiology*; D022242:Pneumococcal Vaccines / Q000009:adverse effects; D012141:Respiratory Tract Infections / Q000150:complications*; D012306:Risk; D020521:Stroke / Q000209:etiology*; D013745:Tetanus Toxoid / Q000009:adverse effects; D006113:United Kingdom; D014552:Urinary Tract Infections / Q000150:complications*; D014612:Vaccines / Q000009:adverse effects*
chemical_list: D007252:Influenza Vaccines; D022242:Pneumococcal Vaccines; D013745:Tetanus Toxoid; D014612:Vaccines