Multiple comorbidities increase the risk of death from invasive pneumococcal disease under the age of 65 years

Risk factors for death from invasive pneumococcal disease (IPD) have not been clearly established in patients aged under 65 years. We aimed to evaluate contributions of host and bacterial factors to the risk of death from IPD in patients aged under 65 years in Japan. In this prospective, observational, multicenter cohort study, patients with IPD (n = 581) aged 6–64 years were enrolled between 2010 and 2017. We investigated the role of host and bacterial factors in 28-day mortality. The mortality rate increased from 3.4% to 6.2% in patients aged 6–44 years to 15.5%–19.5% in those aged 45–64 years. Multivariable analysis identified the following risk factors for mortality: age 45–64 years (hazard ratio [HR], 3.4; 95% confidence interval [CI], 1.6–6.8, p = 0.001), bacteremia with unknown focus (HR, 2.0; 95% CI, 1.1–3.7, p = 0.024), meningitis (HR, 2.1; 95% CI, 1.1–4.0, p = 0.019), underlying multiple non-immunocompromising conditions (HR, 2.6; 95% CI, 1.1–7.4, p = 0.023), and immunocompromising conditions related to malignancy (HR, 2.4; 95% CI, 1.0–5.2, p = 0.039). Pneumococcal serotype was not associated with poor outcomes. Host factors, including age of 45–64 years and underlying multiple non-immunocompromising conditions, are important for the prognosis of IPD. Our results will contribute to the development of targeted pneumococcal vaccination strategies in Japan.