Question: We were wondering, once you have had malaria do you become immune or are you still able to get it?

Julian Rayner answered on 13 Mar 2011:

Really good question, and the answer is actually quite interesting and reveals quite a lot about who gets the disease. People do get immune to malaria, but you have to be infected several times for it to happen. The kind of immunity you get is called “clinical immunity” – it means that you still get infected (if you couldn’t get infected, that would be called sterile immunity), but you don’t get the severe clinical symptoms of the disease. Because it takes quite a few exposures to get this immunity, it is children who get the most severe symptoms, because they haven’t been infected enough to be immune – that is why most of the deaths due to malaria (more than a million each year) are in children under the age of five.

It is possible for adults to lose their immunity. Pregnant women sometimes get quite bad malaria infections, especially in their placenta, which can have a big impact on the developing fetus and sometimes lead to premature birth or low birth weight. You also seem to need continued exposure to keep the immunity up – if you left the malaria region, and then came back a couple of years later, you could get a severe infection again.

Hope this helps – there are lots of details of malaria immunity that we are still working out. However, the fact that people can get immunity to malaria makes us hope that it should be possible to develop a vaccine against it. No vaccine yet though, although people are working very hard.