Most flu vaccines are made by growing the virus in chicken eggs, then inactivating or killing it, a long process.
Flublok, by contrast, consists only of a protein – hemagglutinin – from the virus. The protein is made by putting the gene for hemagglutinin into a virus that infects insect cells. Those cells, from the fall armyworm, are grown in culture and churn out the protein. Neither eggs nor the live virus are used, though viral genetic information is needed.