Step 1: If the vaccine is to be inactivated, the organisms are treated with phenol or formaldehyde. (Heat and phenol or heat and acetone are employed for typhoid fever vaccine).
Step 2: Next, the organisms are separated from the medium through centrifugation and suspended in sterile water or 0.9% sodium chloride for injection.
tissue culture infection doses, the quantity of virus estimated to infect 50% of inoculated cultures
Micrograms of immunogen
International units
D-antigen units
Plaque-forming units for yellow fever vaccine