The immune system is like a smart-phone, complex but elegant in design and equipped with numerous applications (apps) to deal with the microbial challenges of the modern world. Of particular importance are two apps called B-cells and T-cells. The B-cell app neutralizes viruses and the T-cell app kills infected cells. Two notable features of the immune system are specificity and memory. Specificity means that within each app, there are different tools to fight different viruses. For instance, specific groups of B-cells and T-cells are used against flu viruses, and different ones against chickenpox virus. Likewise, different groups of B- and T-cells are used against type A flu and type B flu. Upon infection with a virus like fluA, your immune system searches the app-store for fluA-specific tools within the B-cell and T-cell apps, downloads and uses them against the virus. Memory means that once tools against one flu type are downloaded, they can be readily re-used to fight the same virus, without searching and downloading from the app-store. Installing tools in advance can help to prepare the immune system before infection. Indeed, by vaccination, the immune system learns how to fight viruses. However, because viruses like flu keep changing, the currently installed apps are often not effective at fighting the new flu types. Consequently, the apps need to be updated frequently to keep up with the virus. While the app-store contains different tools against fluA, we don’t know much about the tools available against fluB. Also, the app store doesn’t have any tools labelled for use against both fluA and fluB. We have identified a super-tool within the T-cell app that can be used to fight all flu types and doesn’t require updating. This universally cross-reactive tool is important for flu vaccines that do not need to be updated annually.