Effectiveness of influenza and pneumococcal vaccines in preventing pneumonia 1 development and hospitalization : a prospective cohort study 2 3 Running title : Influenza and pneumococcal vaccines

24 Pneumonia and acute exacerbation of chronic illness are leading causes of influenza-related 25 hospitalization. Therefore, influenza and pneumococcal vaccinations are strongly 26 recommended for adults with comorbidities. Using a hospital-based influenza surveillance 27 system, we performed a multicenter, prospective cohort study of patients visiting emergency 28 rooms with influenza-like illness (ILI) during the influenza epidemic period in 2013–2014. 29 Patients aged ≥ 19 years were enrolled, and clinical data was collected. Multivariate analyses 30 were performed to estimate the effectiveness of influenza and pneumococcal vaccination in 31 preventing pneumonia development and hospitalization. During study periods, 2,262 patients 32 with ILI were registered. Among 2,217 patients with available vaccination records, 31.9% 33 (707 patients) and 9.7% (216 patients) had received influenza and pneumococcal vaccines, 34 respectively. Among patients who had been administered a pneumococcal vaccine, 94.4% had 35 received the 23-valent polysaccharide vaccine (PPV23). The adjusted influenza vaccine 36 effectiveness for preventing pneumonia development and hospitalization was 64.0% (95% 37 confidence interval [CI] = 29% 81%) and 35.0% (95% CI = 12% 52%), respectively. 38 Pneumococcal vaccination did not reduce pneumonia development or hospitalization. In 39 conclusion, influenza rather than PPV23 vaccination may reduce pneumonia development 40 and hospitalization in patients with preceding ILI. 41