Publication date: May 04, 2026
Understanding how clinical symptoms relate to immune responses during major variant transitions remains important for informing post-pandemic surveillance and vaccination strategies. This study compared symptom patterns and SARS-CoV-2-specific anti-RBD IgM and anti-S1 IgG antibody responses among vaccinated individuals infected during the pre-Omicron and Omicron-dominant periods, representing a key phase in the evolution of SARS-CoV-2 population immunity. A retrospective analysis of 216 confirmed COVID-19 cases was performed by evaluating 11 predefined symptoms together with anti-RBD IgM and anti-S1 IgG levels measured at Day-14 after symptom onset, corresponding to the period when humoral antibody responses are detectable following SARS-CoV-2 infection. Participants with breakthrough infection during the Omicron-dominant period reported fewer symptoms overall compared to the pre-Omicron period, with a median of three versus four symptoms, respectively. Cough was the most common symptom during the Omicron period (82. 1%), followed by sore throat (81. 4%) and fever (78. 6%). In contrast, loss of taste or smell was significantly more frequent in the pre-Omicron period (64. 8% versus 22. 9%, p
| Concepts | Keywords |
|---|---|
| Antibodies | antibodies |
| Breakthrough | cough |
| Covid | delta |
| Pandemic | omicron |
| Vaccinated |
Semantics
| Type | Source | Name |
|---|---|---|
| disease | MESH | SARS-CoV-2 Infections |
| pathway | REACTOME | SARS-CoV-2 Infection |
| disease | MESH | breakthrough infection |
| disease | MESH | Cough |
| disease | MESH | sore throat |
| disease | MESH | fever |
| disease | MESH | loss of taste |
| disease | MESH | infection |