BERKELEY, CA (UroToday Inc.) - Studies in animals suggest that chronic inflammation may accelerate atherosclerotic disease and therefore increase the risk of a vascular event. Whether or not acute inflammation secondary to infection or vaccination may lead to an increased risk of myocardial infarction (MI) or stroke is not known. Dr. Liam Smeeth and colleagues from the United Kingdom performed a study to determine the incidence of vascular events after acute infection and vaccination. Their findings were published in the December 16, 2004 edition of the New England Journal of Medicine.

They used the United Kingdom General Practice Research Database, the largest source of continuous data on illness and prescribing habits in the United Kingdom, to find adults who had suffered from a myocardial infarction or stroke. From the database, it was determined whether or not they had had an influenza, tetanus, or pneumococcal vaccination, or had an acute urinary tract or respiratory tract infection. Each subject was followed for a baseline period and then a "risk period", which was 91 days from the time of exposure. A case-series method was used for within-person comparisons.

In 20,486 subjects who had a MI and 19,063 who had a stroke who also received the influenza vaccine, there was no increased risk between the administration of the vaccine and the vascular event. Similarly there was no increased risk in those undergoing tetanus or pneumococcal vaccinations. Interestingly, the incidence of MI and stroke was higher in those who were diagnosed with an acute respiratory infection. The incidence ratio was highest within 3 days of the infection diagnosis, with ratios being 4.95 for MI and 3.19 for stroke. Acute urinary tract infections were also found to have a greater risk for a vascular event within 3 days after the diagnosis (incidence ratio 1.66 for MI and 2.72 for stroke), but the risk was not as high as after a respiratory infection. Recurrent MI and stroke were found to have similar relationships as those for first time MI and stroke.

The authors conclude that acute infection may be associated with an increased risk of vascular events such as MI and stroke, while vaccinations do not appear to carry the same risk.

N Eng J Med 2004; 351:2611-2618