Vaccine effectiveness in symptom and viral load mitigation in COVID-19 breakthrough infections in South Korea.

Objectives: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine effectiveness in coronavirus disease (COVID-19) patients with breakthrough infections has not been established in South Korea. To address this, we assessed the impact of vaccination on symptom occurrence and viral load.

Methods: We performed a retrospective cohort study of 9,030 COVID-19 patients enrolled between February and November 2021.