Baseline characteristics of enrolled participants
| Baseline characteristic | IVIG (n=10) | Placebo (n=8) | All (n=18) | |
| Age at randomisation (years) | Median (IQR) | 5.55 (1.52–11.8) | 4.09 (2.71–9.64) | 4.09 (2.0–11.8) |
| Sex | Male | 4 (40%) | 4 (50%) | 8 (44.4%) |
| Female | 6 (60%) | 4 (50%) | 10 (55.6%) | |
| Ethnicity | White | 8 (80%) | 8 (100%) | 16 (88.9%) |
| Asian | 1 (10%) | 0 (0%) | 1 (5.6%) | |
| Missing | 1 (10%) | 0 (0%) | 1 (5.6%) | |
| History of immunocompromise | No | 9 (90%) | 7 (87.5%) | 16 (88.9%) |
| Missing | 1 (10%) | 1 (12.5%) | 2 (11.1%) | |
| Previous diagnosis of encephalitis | No | 9 (90%) | 7 (87.5%) | 16 (88.9%) |
| Missing | 1 (10%) | 1 (12.5%) | 2 (11.1%) | |
| History of encephalopathic illness | No | 9 (90%) | 7 (87.5%) | 16 (88.9%) |
| Missing | 1 (10%) | 1 (12.5%) | 2 (11.1%) | |
| Pre-existing diagnosis of epilepsy | No | 9 (90%) | 7 (87.5%) | 16 (88.9%) |
| Missing | 1 (10%) | 1 (12.5%) | 2 (11.1%) | |