The established approach is to grow weakened viruses in chicken eggs—or more recently in mammalian or insect cells—and extract the desired pieces. The process can take four to six months to get the right antigens for familiar viruses that change every year, such as influenza. It can take multiple attempts over years for a new germ. That is far too slow to combat a virus that has already spread to pandemic proportions.

Instead labs are turning to gene-based vaccines. Scientists use information from the genome of the virus to create a blueprint of select antigens. The blueprint is made of DNA or RNA—molecules that hold genetic instructions. The researchers then inject the DNA or RNA into human cells. The cell’s machinery uses the instructions to make virus antigens that the immune system reacts to. Cells respond to the instructions as a normal part of their daily existence. This is the same trait infectious viruses exploit; they cannot reproduce on their own, so they use a cell’s machinery to make copies of themselves. They burst out of the cell and infect more cells, widening the infection.

Virtually all the labs want to find a way to train human cells to make an antigen called the spike protein.