| Background | Effective | Proportion (%) |
| Previous hospitalization | 68 | 25.09 |
| Congenital heart disease | 12 | 4.43 |
| sickle cell anemia | 4 | 1.48 |
| Epilepsy | 2 | 0.74 |
| Asthma | 1 | 0.37 |