Pneumococcal vaccine does not reduce MI, stroke risk
MedWire News: US researchers report finding no evidence that pneumococcal vaccination is associated with reduced risk for acute myocardial infarction (MI) or stroke.
Their results contrast with those from an earlier case–control study suggesting a protective role of pneumococcal vaccine against these cardiovascular events.
Multiple studies have shown that vaccination against influenza can reduce the risk for recurrent MI, sudden cardiac death, cardiac hospital admissions, need for revascularization, and stroke, explain Hung Fu Tseng, from Kaiser Permanente Southern California in Pasadena, and colleagues.
The effect of pneumococcal polysaccharide vaccine on vascular events has not been studied extensively and remains controversial, however.
To investigate further, the researchers studied the incidence of acute MI and stroke according to pneumococcal vaccine exposure in 84,170 participants of the California Men’s Health Study, a general health survey. Vaccination records were obtained via the Kaiser Immunization Tracking System.
Participants were followed-up for a mean of 4.7 years, during which time there were 2705 cases of acute MI and 1134 stroke cases, and 47,861 participants had no pneumococcal vaccine doses, 30,817 had one dose, 5018 had two doses, and 474 had three or more doses.
Analysis showed that there were 1211 first MI events in 112,837 vaccinated person-years (10.73 per 1000 person-years) compared with 1494 first MI events in 246,170 unvaccinated person-years (6.07 per 1000 person-years).
For stroke, there were 651 events in 122,821 vaccinated person-years (5.230 per 1000 person-years) compared with 483 events in 254,541 unvaccinated person-years (1.90 per 1000 person-years).
After propensity-score adjustment, the multivariable hazard ratio for MI associated with pneumococcal vaccination was a nonsignificant 1.09; similarly the corresponding hazard ratio for stroke was nonsignificant, at 1.14.
Tseng and colleagues report their findings in the Journal of the American Medical Association. They explain that pneumococcal vaccine is currently recommended to adults aged 65 years or older who may be at risk for pneumococcal infection due to underlying chronic conditions including heart failure or cardiomyopathy, chronic pulmonary diseases, and diabetes.
Not surprisingly, therefore, patients who were vaccinated in the study were generally older and had more comorbid chronic conditions than those who were not.
But in a related editorial Mohammed Madjid and Daniel Musher, respectively from Texas Heart Institute and Baylor College of Medicine in Houston, highlight that there were “substantial” differences between the two groups and that the multivariable and additional propensity score adjustment may not have been adequate to account for confounding.
Although controversy over the efficacy of pneumococcal vaccination per se persists, they write, “numerous studies have shown that the vaccine is associated with a reduction in risk for invasive pneumococcal infection by 30% to 60%.”
Until rigorous data from clinical trials are available regarding its ability to prevent cardiovascular events, they conclude that “physicians should strictly adhere to available guidelines for optimizing vaccination rates in recommended target groups, because these rates are still far from optimal.”
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By Caroline Price