# Epidemiological features of the 2024 pertussis outbreak in Gyeonggi Province, Korea

## TL;DR

In 2024, a pertussis outbreak in Gyeonggi Province, Korea, mainly affected children and adolescents, with unvaccinated individuals facing higher healthcare needs.

## Contribution

The study reveals that unvaccinated or undocumented vaccination status in adolescents correlates with delayed diagnosis and increased hospitalization during pertussis outbreaks.

## Key findings

- 89.8% of pertussis cases occurred in individuals under 20 years, especially those aged 10-14 years.
- Unvaccinated individuals under 20 had higher hospitalization rates (11.7%) compared to vaccinated groups (5.9%).
- Adults had higher hospitalization and emergency visit rates than children and adolescents.

## Abstract

In 2024, Korea experienced a nationwide pertussis epidemic, with Gyeonggi Province accounting for nearly one-third of reported cases. This study investigated the epidemiological characteristics of the outbreak and explored the association between vaccination history and healthcare utilization.

We analyzed 14,275 pertussis cases reported in Gyeonggi Province in 2024 using de-identified national surveillance data. Comparisons were performed by age group (<20 vs. ≥20 years) and vaccination status (<20 years). The chi-square and Mann–Whitney U tests were used, and effect sizes were assessed using Cramér’s V.

Of all cases, 89.8% occurred in individuals <20 years, particularly those aged 10-14 years. Children and adolescents were more often involved in clusters and had more identified contacts than adults, whereas adults had higher rates of hospitalization (13.2 vs. 5.9%) and emergency visits (4.4 vs. 0.9%; p<0.001). Among individuals <20 years, hospitalization was more common in the unvaccinated or unknown group (11.7%) than in the fully (5.9%) or partially vaccinated (5.5%) groups (p=0.045).

The epidemic was concentrated in school-aged populations, particularly adolescents. While vaccination status showed a limited association with healthcare utilization, individuals who were unvaccinated or had an undocumented vaccination history experienced delayed diagnosis and higher care needs. These findings highlight the importance of strengthening adolescent-focused vaccination strategies and preparedness for future pertussis outbreaks.