Associations between Pneumococcal Vaccinationand Adverse Outcomes in Patients with Suspected Acute Coronary Syndrome

Abstract

Background: Although pneumococcal vaccination prevents the most common pneumonia of bacterial etiology, its associations without comes of Acute Coronary Syndrome (ACS) are unknown. Methods: This is a prospective cohort study of 1436 patients hospitalized with suspected ACS/non-ST elevation MI that were eligible for pneumococcal vaccination. Primary outcomes were death and subsequent Myocardial Infarction (MI) within 6-months of the index hospitalization. We used Cox regression to assess associations between pneumococcal vaccination and outcomes, adjusting for influenza vaccination and relevant clinical covariates. We also utilized propensity scores to adjust for potential confounding. Results: Overall, 937 (65.3%) patients received pneumococcal vaccination either prior to or during the index hospitalization. Unvaccinated patients had higher mortality (26.9% vs 7.9%; p < 0.001) and non-significantly higher frequency of subsequent MI (7.4% vs 3.5%; p = 0.06).Compared to patients who did not receive either pneumococcal or influenza vaccination, the unadjusted Hazard Ratio (HR) of death was significantly lower for those who received only pneumococcal vaccination (HR = 0.13; 95% CI 0.07 - 0.23) or both vaccinations (HR = 0.66, 95% CI 0.47 - 0.92), and significantly higher for patients who received only influenza vaccination (HR = 1.88, 95% CI 1.33 - 2.64). The corresponding HRs and 95% CIs for subsequent MI were 0.58 (95% CI 0.32 - 1.03) for pneumococcal vaccination only, 0.41 (95% CI 0.21 - 0.80) for both vaccinations and 0.97 (95% CI 0.48 - 1.95) for influenza vaccination alone. These remained unchanged after covariate or propensity score adjustment. Conclusions: Among patients hospitalized with suspected ACS, pneumococcal vaccination, with or without influenza vaccination, was associated with significantly lower risk of mortality within 6 months.