# Community-acquired bacterial meningitis in Southern Sweden 2013–2023: a population-based study of incidence, aetiology and diagnostic yield

## TL;DR

This study examines the incidence and causes of bacterial meningitis in southern Sweden from 2013 to 2023, finding that pneumococcal meningitis is the main cause and that many cases are preventable with current vaccines.

## Contribution

The study provides updated insights into CABM trends and vaccine-preventable serotypes in southern Sweden.

## Key findings

- The mean incidence rate of CABM was 1.63 per 100,000 person-years, with a declining trend observed.
- Streptococcus pneumoniae was the most common pathogen, responsible for 46.7% of cases.
- 63.6% of pneumococcal meningitis cases were caused by serotypes included in current vaccines.

## Abstract

Despite advances in medical care, bacterial meningitis still poses a considerable health issue from a global perspective. An ageing population and increasing development and use of vaccines are likely to affect the incidence and aetiology. The aim of this study was to describe the incidence and aetiology of community-acquired bacterial meningitis (CABM) in our setting, as well as the serotypes of Streptococcus pneumoniae and Neisseria meningitidis causing CABM, in relation to available vaccines.

Patients of all ages with CABM in southern Sweden 2013–2023 were included. Patients were identified through records of cerebrospinal fluid tests from the Department of Clinical Microbiology, and through International Classification of Diseases 10 codes for bacterial meningitis. Age-standardised incidence rates were calculated based on the European Standard Population 2013.

During the study period, 244 episodes of CABM in 238 individuals were identified. Definitive aetiology could be established in 93% of episodes. Mean incidence rate was 1.63 per 100,000 person-years, with a trend of declining incidence during the study period. Streptococcus pneumoniae was the most common pathogen, accounting for 46.7% of episodes. 63.6% of the episodes of pneumococcal meningitis were caused by serotypes included in current vaccines.

Pneumococcal meningitis is the primary driver of incidence and trends of all-cause community-acquired bacterial meningitis in southern Sweden. Further studies are warranted to investigate how vaccination could influence both disease incidence and shifts in serotype distribution, while also identifying optimal patient populations for targeted interventions.

The online version contains supplementary material available at 10.1007/s10096-025-05247-w.