Rationale and design of the CAPAMIS study: Effectiveness of pneumococcal vaccination against community-acquired pneumonia, acute myocardial infarction and stroke

Background: The 23-valent polysaccharide pneumococcal vaccine (PPV-23) is recommended for elderly and high-risk people, although its effectiveness is controversial. Some studies have reported an increasing risk of acute vascular events among patients with pneumonia, and a recent case-control study has reported a reduction in the risk of myocardial infarction among patients vaccinated with PPV-23. Given that animal experiments have shown that pneumococcal vaccination reduces the extent of atherosclerotic lesions, it has been hypothesized that PPV-23 could protect against acute vascular events by an indirect effect preventing pneumonia or by a direct effect on oxidized low-density lipoproteins. The main objective of this study is to evaluate the clinical effectiveness of PPV-23 in reducing the risk of pneumonia and acute vascular events (related or nonrelated with prior pneumonia) in the general population over 60 years. Methods/Design: Cohort study including 27,000 individuals 60 years or older assigned to nine Primary Care Centers in the region of Tarragona, Spain. According to the reception of PPV-23 before the start of the study, the study population will be divided into vaccinated and nonvaccinated groups, which will be followed during a consecutive 30-month period. Primary Care and Hospitals discharge databases will initially be used to identify study events (community-acquired pneumonia, hospitalisation for acute myocardial infarction and stroke), but all cases will be further validated by checking clinical records. Multivariable Cox regression analyses estimating hazard ratios ( adjusted for age, sex and comorbidities) will be used to estimate vaccine effectiveness. Discussion: The results of the study will contribute to clarify the controversial effect of the PPV-23 in preventing community-acquired pneumonia and they will be critical in determining the posible role of pneumococcal vaccination in cardiovascular prevention.