Pneumococcal Meningitis in Adults in 2014-2018 After Introduction of Pediatric 13-valent Pneumococcal Conjugate Vaccine in Japan

We assessed the impact of pediatric 13-valent pneumococcal conjugate vaccine (PCV13) on pneumococcal meningitis in adults in Japan in 2014-2018 by comparing epidemiological characteristics of adults with invasive pneumococcal disease with (n=222) and without (n=1,258) meningitis. Pneumococcal meningitis annual incidence in 2016 - 2018 was 0.20–0.26 cases/100,000 population . Age (p<0.001) and case fatality rate (p=0.003) were significantly lower in patients with meningitis than in those without meningitis. Meningitis risk was higher in asplenic/hyposplenic or splenectomized patients (adjusted odds ratio [aOR] 2.29, 95% CI 1.27–4.14), for serotypes 10A (aOR 3.26, 95% CI 2.10–5.06) or 23A (aOR 3.91, 95% CI 2.47–6.19), but lower for those aged ³65 years (aOR 0.59, 95% CI 0.44–0.81). PCV13 had an indirect effect on nonmeningitis, but its impact on meningitis was limited because of an increase in non-PCV13 serotypes. Of meningitis isolates, 78 (35.1%) and 3 (1.4%) were penicillin G- and ceftriaxone-resistant. We also confirmed association of the pbp1b A641C mutation with meningitis (aOR 2.92, 95% CI 1.51–5.65).