Yellow Fever Vaccine »Yellow Fever Vaccine conforms to the regulations of the FDAconcerning biologics (see Biologics á1041ñ).It is the attenuated strain that has been tested in monkeys for viscerotropism,immunogenicity,and neurotropism of living yellow fever virus selected for high antigenic activity and safety.It is prepared by the culturing of the virus in the living embryos of chicken eggs,from which a suspension is prepared,processed with aseptic precautions,and finally dried from the frozen state.It meets the requirements of the specific mouse potency test in titer of mouse LD50(quantity of virus estimated to produce fatal specific encephalitis in 50%of the mice)or the requirements for plaque-forming units in a suitable cell culture system,such as a Vero cell system for which the relationship between mouse LD50and plaque-forming units has been established,in which cell monolayers in 35mm petri dishes are inoculated for a specified time with dilutions of Vaccine,after which the dilutions are replaced with 0.5%agarose-containing medium.Following adsorption and incubation for five days an overlay is added of the 0.5%agarose medium containing 1:50,000neutral red and the plaques are counted on the sixth day following inoculation.It is sterile,and contains no human serum and no antimicrobial agent. Yellow Fever Vaccine is constituted,with Sodium Chloride Injection containing no antimicrobial agent,just prior to use. Packaging and storage— Preserve in nitrogen-filled,flame-sealed ampuls or suitable stoppered vials at a temperature preferably below 0but never above 5,throughout the dating period.Preserve it during shipment in a suitable container adequately packed in solid carbon dioxide,or provided with other means of refrigeration,so as to ensure a temperature constantly below 0. Expiration date— The expiration date is not later than 1year after date of issue from manufacturer's cold storage (-20,1year). Labeling— Label it to state that it is to be well shaken before use and that the constituted vaccine is to be used entirely or discarded within 1hour of opening the container.Label it also to state that it is the living yellow fever vaccine virus prepared from chicken embryos and that the dose is the same for persons of all ages,but that it is not recommended for infants under six months of age. Auxiliary Information— Staff Liaison:Tina S.Morris,Ph.D.,Senior Scientist Expert Committee:(VVI)Vaccines,Virology,and Immunology USP28–NF23Page 2043 Phone Number:1-301-816-8397