Pneumococcal Vaccine Does Not Reduce Risk of MI, Stroke in Men

Pneumococcal vaccination does not reduce the risk of acute myocardial infarction (MI) or stroke in men ≥45 years of age, according to a study published in the Journal of the American Medical Association [2010;303(17):1699-1706].

A prospective cohort study was performed with data collected by the California Men’s Health Study, which is a multiethnic cohort of men enrolled in Kaiser Permanente Northern California and Kaiser Permanente Southern California health plans. The analysis included 84,170 participants between the ages of 45 and 69 years, recruited from January 2002 to December 2003 and followed until December 31, 2007.

A questionnaire was used to determine demographics, family history of cancer, personal health and lifestyle, existing health conditions, medication or drug use, physical activity, tobacco use, diet or supplement use, country of origin, duration of US residency, income, sexual orientation, and general health. Vaccination records were tracked through the Kaiser Immunization Tracking System. Incidences of acute MI and stroke were identified through corresponding International Classification of Diseases, Ninth Revision codes in electronic medical records.

The relationship between acute MI and stroke rates and vaccination status was adjusted for with a propensity score that took into account age, race/ethnicity, region (Northern vs Southern California), household income, education, body mass index (BMI), cigarette smoking, physical activity level, being sedentary >6.5 hours/day outside of work, alcohol consumption, number of influenza vaccinations received, total calorie intake, fat intake, fruit and vegetable consumption, history of diabetes, history of high blood pressure, history of high cholesterol, history of peripheral artery disease, history of other heart diseases, history of stroke, history of acute MI, and number of outpatient visits in the 5 years prior to baseline.

The analysis identified 2705 cases of acute MI and 1134 stroke cases. Subjects who had not received the pneumococcal vaccine had a shorter length of follow-up compared with those who had received the vaccine. Subjects who had received the vaccine were significantly older than those who had not received the vaccine. Other factors, including region, race/ethnicity, household income, education, and BMI, also significantly influenced the likelihood of having received a pneumococcal vaccine.

The incidence of acute MI or stroke was positively associated with an increasing number of pneumococcal vaccines. Acute MI occurred at a rate of 2.0% in unvaccinated subjects versus rates of 4.6%, 5.5%, and 5.3% in subjects who had received 1, 2, or ≥3 doses of vaccine, respectively. Stroke rates were 0.7% in the unvaccinated group versus 2.1%, 2.8%, and 3.0% in subjects who had received 1, 2, or ≥3 doses of vaccine, respectively.

After adjustment with propensity score, the investigators found that the pneumococcal vaccine did not demonstrate a protective effect against acute MI and stroke. The study authors cited previous data that did demonstrate a protective effect with the vaccine, suggesting that their use of a propensity score may have reduced the likelihood of confounding factors in the analysis.

The authors noted that the study findings could be limited due to the fact that acute MI and stroke cases were identified with diagnostic codes in electronic medical records, and misclassifications were possible. They added that the association between pneumococcal vaccine and acute MI and stroke risk in women and very elderly populations was not determined in their analysis.—Kristina Woodworth