Methods: This was a national nested case-control study of older Veterans (≥50 years of age) unvaccinated within the past 5 years with positive S. pneumoniaeblood, cerebrospinal fluid, or respiratory cultures admitted to Veterans Affairs facilities between January 1, 2002 and December 31, 2011. Using logistic regression, we quantified 30-day mortality (cases: not alive 30 days after culture; controls: alive at 30 days) by comparing individual pneumococcal disease risk factors present within one year prior to culture (age ≥65, alcoholism, diabetes mellitus, heart disease, immunodeficiency, liver disease, respiratory disease, smoking) and all possible combinations of risk factors to those without risk factors.
Results: We identified 9,730 serious pneumococcal infections (1,764 cases and 7,966 controls) in 9,468 unvaccinated individuals, with a 30-day mortality of 18.6%. Primary infection types included pneumonia (62%), bacteremia (26%), and bacteremic pneumonia (11%). In addition to the 8 individual risk factors, there were 247 unique combinations of risk factors, with 85% (n=1,496) and 74% (n=5,898) of cases and controls having at least two risk factors, respectively. Beginning with two risk factors, risk of mortality increased with each addition of a risk factor up to a total of 6 risk factors (two: OR 2.01, CI 1.47-2.75; three: OR 2.71, CI 1.99-3.69; four: OR 3.27, CI 2.39-4.47; five: OR 3.63, CI 2.60-5.07; six: OR 4.23, CI 2.69-6.65). The addition of each risk factor increased risk of mortality by an average of 56%.
Conclusion: Among older adults with serious pneumococcal disease, risk of 30-day mortality more than doubled from 2 to 6 disease states present. Pneumococcal disease prevention is therefore essential to minimize the deleterious effects of acute infection in the setting of multiple disease states.
K. Laplante, Merck (Cubist): Consultant and Scientific Advisor , Research support
Pfizer: Consultant and Scientific Advisor , Research support
Allergan (Forest): Consultant and Scientific Advisor , Research support
The Medicines Company: Consultant and Scientific Advisor , Research support
Melinta: Consultant and Scientific Advisor , Research support
A. Caffrey, Pfizer: Research , Research grant
Merck (Cubist): Research , Research grant