Fauci is more excited about something called a recombinant protein vaccine, which does not rely on growing viruses, even though it is cell-based. At Protein Sciences, a small Connecticut biotech firm, researchers isolate the gene for the flu virus’s surface proteins and insert it into an entirely different species of virus, called a baculovirus. The baculovirus infects insect cells and causes them to make huge amounts of the surface proteins, which the company uses to make Flublok, the only recombinant protein flu vaccine currently available.