Disease Trends and Mortality From Invasive Pneumococcal Disease: A Long-Term Population-Based Study

Streptococcus pneumoniae is a major global cause of invasive pneumococcal disease (IPD) and death. Introduction of the pneumococcal conjugate vaccine (PCV) has led to substantial declines in IPD incidence in many countries. Long-term, population-based studies on mortality trends among survivors of acute IPD are scarce.

Data encompassing all individuals diagnosed with IPD in Iceland from 1975 to 2020 were analyzed. Diagnosis required a positive blood or cerebrospinal fluid culture. 30-day and 5-year mortality rates were assessed across 3 decades (1985-2014), adjusting for multiple covariates. Additionally, age-standardized all-cause mortality rates were compared between patients with IPD and the general population.

The cohort included 1463 patients of all ages. Invasive pneumococcal disease incidence peaked in 1995-2004 and declined significantly thereafter (P < .001). Serotype 7F was the most prevalent. No improvement in short-term mortality at 30 days was detected over time (P = .98). A modest improvement in 5-year mortality was observed, although this did not reach statistical significance (P = .076). Even when early deaths were excluded, the ASR for all-cause mortality in patients with IPD was 2.6 times higher than in the general population (0.021 vs 0.008 per person-year).

IPD incidence declined substantially over time, particularly following the introduction of the 10-valent PCV in 2011, yet short-term mortality remained unchanged. A modest improvement in long-term mortality was observed, possibly reflecting advances in chronic disease management. Invasive pneumococcal disease survivors face significantly elevated long-term mortality compared to the general population. Targeted interventions are needed to reduce short-term mortality associated with IPD.