Association between sore throat and early immune responses against COVID-19 before and after the emergence of the Omicron variant

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Background: Sore throat is a prevalent symptom of coronavirus disease 2019 (COVID-19), particularly when caused by the Omicron variants. However, the association between sore throat and immune responses to different severe acute respiratory syndrome coronavirus 2 variants remains unclear. This study aimed to elucidate the characteristics of immune responses associated with sore throat in patients with COVID-19 before and after the emergence of Omicron. Methods: In this prospective observational study, we enrolled patients with COVID-19 hospitalized between December 2020 and April 2022, which covered the pre-Omicron and Omicron (BA.1 variant) endemic periods. Sore throat was assessed using a daily questionnaire, including an analog scale for sore throat grade (0 to 3) from admission until discharge. Serum levels of immune indicators were assessed using enzyme-linked immunosorbent assay. Results: 42%, P<0.005). Sore throat was associated with nasopharyngeal viral load, interleukin-6 (IL-6)/interferon-α (IFN-α) levels in participants infected with preceding variants, whereas, it was associated with age, the body mass index, and interferon-λ1 (IFN-λ1) in participants infected with Omicron. Conclusions: Infection with the Omicron variant is characterized by increased sore throat frequency and altered associations between sore throat and several immune indicators, including IFN-α, IL-6, and IFN-λ1.