Some people are more prone to infection than others. One answer could be to dose them with the molecules that their immune systems cannot make.

“Researchers are studying how different versions of certain genes could cause some people to succumb to infection whereas others are left relatively unscathed. They thus hope to explain not only why some people can be infested with virulent microbes without contracting a disease (whereas others become ill even though they are less infected) but also why such patterns run in families and in ethnic groups. Laurent Abel and Jean-Laurent Casanova of the Necker Medical School in Paris have found that a different version of a single gene out of the 25,000 or so in the human genome can make all the difference to whether or not a person suffers from many common diseases.”

(via The Economist)

(see also “A Cancer-Proof Mouse” via The Daily Galaxy)