Much like a viral contagion, misinformation can spread rapidly from one mind to another. Moreover, once lodged in memory, falsehoods are difficult to correct. Inoculation theory offers a natural basis for developing a psychological ‘vaccine’ against the spread of fake news and misinformation. Specifically, in a series of lab and field studies, I’ll show that it is possible to pre-emptively “immunize” people against disinformation about a wide range of topics by pre-exposing them to severely weakened doses of the techniques that underlie its production. This process of ‘prebunking’ helps people cultivate cognitive antibodies in both simulated and real social media environments. I’ll showcase several interventions we developed and evaluated—with public health authorities and social media companies—to help citizens around the world recognize and resist unwanted attempts to influence and mislead.