The vials, now in three hulking freezers outside Dr. Mina’s lab, are at the center of a pilot project for what he and his collaborators call the Global Immunological Observatory. They envision an immense surveillance system that can check blood from all over the world for the presence of antibodies to hundreds of viruses at once. That way, when the next pandemic washes over us, scientists will have detailed, real-time information on how many people have been infected by the virus and how their bodies responded.

It might even offer some early notice, like a tornado warning. Although this monitoring system will not be able to detect new viruses or variants directly, it could show when large numbers of people start acquiring immunity to a particular kind of virus.

The human immune system keeps a record of pathogens it has met before, in the form of antibodies that fight against them and then stick around for life. By testing for these antibodies, scientists can get a snapshot of which flu viruses you have had, what that rhinovirus was that breezed through you last fall, even whether you had a respiratory syncytial virus as a child. Even if an infection never made you sick, it would still be picked up by this diagnostic method, called serological testing.