The spleen, which is an organ in the abdomen, used to be a bit of a mystery. Now it's known to play a very important part in the body's fight against infection. It purifies the blood and stimulates the immune system, and is particularly important in preventing some types of infection. Trauma to the abdomen (which often occurs in a road traffic accident) can cause the spleen to split open, leading to haemorrhage. The spleen may then need to be taken out (although with improvements in surgical techniques it's becoming increasingly possible to repair damaged spleens). The spleen can also be badly damaged by sickle cell anaemia and some other conditions.

You can live without your spleen, but you're then more vulnerable to infection, especially with a bacterium called the pneumococcus (or Streptococcus pneumoniae to give it its proper name). This bacterium can cause several different infections including pneumonia, meningitis and septicaemia (blood poisoning), which may be rapidly fatal.

Fortunately, as your husband's colleague has said, there's a vaccine against the pneumococcus. It's vital that anyone who has lost their spleen is immunised with it.

The vaccine, which doesn't contain live bacteria and so usually causes only minor side effects, is 60 per cent to 70 per cent effective in protecting against pneumococcal infections and lasts up to ten years (although doctors often advise a blood test after just five years to check that you're still immune). Some people, especially those under the age of 20, will also need to take long-term antibiotics to guard against infection.

For further information, contact: The Splenectomy Trust, c/o Swinbrook Post Office, Swinbrook, Oxfordshire OX1 4DX

The Department of Health also recommends others who may be vulnerable to the pneumococcus are vaccinated. These include the chronically sick, and those whose immune system is damaged or suppressed (such as those with HIV and those on steroids).

This article was last medically reviewed by Dr Trisha Macnair in July 2008