Although patients who had previously had a myocardial infarction were excluded from the study by François Lamontagne and colleagues,1 some patients who had received the pneumococcal vaccine and had had an acute ischemic event were excluded as well. For example, if a vaccinated patient had had a myocardial infarction 1 month before being admitted to 1 of the medical wards of the hospital for another reason, he would not have participated in the study. Thus, the supposed protective effect of the vaccine would not have been measured.
The authors did not report the number of risk factors (hypertension, dyslipidemia and diabetes) for each patient in the study. There is an increase in cardiovascular risk for men and women who have 2 or 3 risk factors.2,3 The absence of stratification may have impaired the comparison between the groups. Furthermore, there are other relevant factors, such as a positive family history, that were not evaluated in the study.
It is known that antibody levels decrease 5–10 years after receipt of the pneumococcal polysaccharide vaccine, and this occurs more quickly in some groups than others.4 This does not fit with the authors' finding that pneumococcal vaccination appeared to have a greater protective effect over time. Given these concerns, the relation between the use of pneumococcal vaccine and reduction of myocardial infarction risk appears to be suspect, despite the authors' suggestion of a strong causal association.
Footnotes
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Competing interests: None declared.