A Christian Science perspective
Who wouldn't want to be immune to flu or any other disease making the headlines? One technique is to be careful to wash one's hands frequently and to stay away from people who are coughing. Another option may be a vaccine that's designed to provide immunity for the particular disease that may be threatening.
What if there were instead a preventative for some current contagion, an opportunity to experience unlimited immunity to diseases of all kinds? While one might rightfully doubt the likelihood of finding such a material remedy, it's possible to look in another direction, to a spiritual source, for freedom from contagion.
In "Science and Health with Key to the Scriptures," Mary Baker Eddy wrote, "Christian Science reveals God, not as the author of sin, sickness, and death, but as divine Principle, Supreme Being, Mind, exempt from all evil" (p. 127). The eternal identity of every man, woman, and child, is exempt from evil of every nature, including what are called contagious diseases.
But to gain this exemption, it's important not only to recognize that we are spiritual but to live our spirituality. To do this would include expressing qualities such as love, honesty, goodness, intelligence, instead of indulging in what are called mortal, or unspiritual, thoughts and behavior that are motivated by fear, hatred, anger, and jealousy. To whatever degree we are able to treat others with kindness, to resist resentment and other negative characteristics, we contribute to rendering ourselves immune to disease. This is true because in Spirit, there is no disease, and each of us, as a child of Spirit, is already exempt from disease. What makes us vulnerable is when we forget this and start thinking of ourselves or others in material terms. In other words, we become fearful of disease or some other situation, or we respond to individuals with anger, envy, or hatred. Such thought and behavior bring us into the mortal realm, where disease is the norm. But by acknowledging that we live within the spiritual atmosphere, where divine Love reigns, we are accepting the spiritual nature that is ours from God, and with it, the immunity God provides.