Considering that most participants in the INCOV cohort were sampled multiple times after symptom onset, we modelled the participant-specific effects and time-specific effects to the IL2-AIS scores in the INCOV cohort (see Methods), which confirmed the progressive decline during the first 90 days post-infection in CD4+ T, CD8+ T and NK cells, followed by a slow recovery (Additional file 3: Fig. S4). Here, CD4 is linked to infection.