Back in the summer, Dr. Michael Mina made a deal with a cold storage company. With many of its restaurant clients closed down, the firm had freezers to spare. And Mina, a public health researcher at the Harvard T.H. Chan School of Public Health, had a half-million vials of plasma from human blood coming to his lab from across the country.

The vials are now at the center of a pilot project for what he and his collaborators call the Global Immunological Observatory. They envision a 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 real-time information on how many people have been infected and how their bodies responded.

It might even offer some early notice. 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. Even if an infection never made you sick, it would still be picked up by this diagnostic method, called serological testing. "We're all like little recorders," Mina said.

This type of readout from the immune system is different from a test that looks for an active infection. The immune system starts to produce antibodies one to two weeks after an infection begins, so serology is retrospective.

Serology uncovers things that virus testing does not, said Derek Cummings, a public health researcher. With a large database of samples and clinical details, scientists can see patterns emerge in how the immune system responds in someone with no symptoms compared with someone struggling to clear the virus.

Mina estimated that such an observatory would cost about $100 million to get off the ground. He pointed out that, according to his calculations, the federal government has allocated more than twice that much to diagnostics company Ellume to produce enough rapid COVID tests to cover U.S. demand for only a handful of days. A pathogen observatory, he said, is like a weather forecasting system that draws on sensors around the globe.

"Had we had it set up in 2019, then when this virus hit the U.S., we would have had ready access to data that would have allowed us to see it circulating in New York City, for example, without doing anything different," Mina said.