The risk of infection is much higher among children than adults. The risk also appears to decline with time. Some doctors believe that other organs eventually take over the role of spleen completely. The pneumococcus bacteria, which can cause pneumonia and other illnesses, is of particular concern. Pneumonia vaccines are recommended for people who have had a splenectomy.
Flu shots are probably a good idea, too.
Although the flu is a viral infection, it increases the risk of catching a secondary bacterial infection. Now, here is where the common sense comes back in the picture. Given the greater susceptibility to infection, people without spleens should try to keep their immune systems as healthy and strong as possible. Exercising, eating a healthy diet, reducing stress and getting plenty of rest will all help the immune system. Drinking in excess of the moderate range is likely to tax the immune system, rather than enhance it.