The spleen plays a significant role in the defence against infections, especially infections caused by encapsulated bacteria, such as Streptococcus pneumoniae. In case of (functional) asplenia, a fulminant sepsis with a high mortality rate may develop in a short time. Preventive measures are therefore recommended for people without a spleen or who have a dysfunctional spleen. A dysfunctional spleen may be present in diseases such as sickle cell anaemia, ulcerative colitis, Crohn's disease and coeliac disease. Preventive measures consist of vaccinations, antibiotics and patient education. Unfortunately, however, it has been shown that these preventive measures are not adequately followed. Currently, a Dutch guideline for healthcare providers is being developed.