Work

Incidence of respiratory infections after the COVID-19 pandemic (2023-2024) and its association of vaccination among entire populations in Korea

Year: 2025

Type: article

Abstract: Objectives We aimed to investigate nationwide trends in respiratory infections during and after the COVID-19 pandemic and to evaluate the risk according to the COVID-19 vaccine dose. Methods Using the database, which integrates the insurance claims and vaccination records for the entire Korean population ( N = 51,645,564), trends were assessed using SARIMAX models. We assessed associations between the doses that have been received until June 1, 2023, and the onset of respiratory infections, using Cox hazard and Fine-Gray models. Results Compared with pre-pandemic levels (2017-2019), influenza like illness (ILI) and pneumonia incidences dropped by over 90% during 2020-2021, followed by a resurgence of upper respiratory tract infection (URI) and common cold in 2023-2024. Pertussis incidence rose 46-fold above expected levels in late 2023. Individuals (≥4 th dose) had lower risks of ILI (adjusted hazard ratio: 0.55 [95% CI: 0.54-0.57]) and pertussis (0.06 [0.04-0.08]), but higher risks of URI (1.32 [1.32-1.33]) and common cold (1.63 [1.62-1.64]), compared with unvaccinated or partially vaccinated. Conclusion With changes in respiratory infection patterns, COVID-19 vaccination may be differentially associated with respiratory infections in the post-pandemic era, reflecting shifts in population-level immunity and highlighting the need for adaptive public health strategies.

Source: International Journal of Infectious Diseases

DOI: 10.1016/j.ijid.2025.108194