Association between pneumococcal vaccination and mortality risk in critically ill patients with acute myocardial infarction: A retrospective cohort study using a large clinical database.

BACKGROUND: Critically ill patients with acute myocardial infarction (AMI) carry a substantial mortality burden. Pneumococcal vaccination reduces the risk of invasive pneumococcal disease; however, the association between pneumococcal vaccination recorded during hospitalization and outcomes in critically ill patients with AMI remains unclear. OBJECTIVES: To examine the association between in-hospital pneumococcal vaccination records and 30-day and 90-day all-cause mortality after intensive care unit (ICU) admission. METHODS: This retrospective cohort study used the Medical Information Mart for Intensive Care IV (MIMIC-IV) version 3.1 database. Adult patients with AMI admitted to the ICU for the first time were included, excluding those with an ICU stay <24 h. Patients were classified as vaccinated or unvaccinated according to pneumococcal vaccination records during hospitalization. Time-dependent Cox models were applied, with sensitivity analyses, 6-hour landmark analysis, propensity score matching (PSM), subgroup analyses, and vaccine-type analyses. RESULTS: Among 5638 patients, 1447 were vaccinated and 4191 were unvaccinated. In the fully adjusted model, pneumococcal vaccination was associated with lower 30-day mortality (HR = 0.69, 95% CI 0.58-0.83, P < 0.001) and 90-day mortality (HR = 0.75, 95% CI 0.65-0.86, P < 0.001). Sensitivity and PSM analyses yielded consistent results. CONCLUSION: Pneumococcal vaccination recorded during hospitalization was associated with lower 30-day and 90-day mortality in critically ill patients with AMI. These exploratory findings require prospective validation.