This archive contains 224 antisera including antisera to many of the viruses listed and available for study. It contains, also, antisera to viruses no longer in our possession or found to be non-viable that are not listed in the Archive. Some of the properties of the antisera bearing F designations can be inferred by reference to the file (F) numbers of the immunizing viruses. For example, antiserum to an antigenically hybrid virus will also be hybrid with respect to its ability to recognize either HA or NA antigens of either of the two parental viruses.

Virtually all the antisera listed were produced by intravenous injection of New Zealand rabbits with virus in the form (usually) of gradient purified allantoic fluid virus or (less frequently) semi-purified allantoic fluid from chick embryos. These sera are "hyper-immune" in the sense that they represent secondary response antisera to a second (boosting) i.v. injection of virus administered approximately 40 days after the initial priming dose of virus. The sera listed here are final bleedings obtained 47-61 days after initial priming injections and 7 to 14 days after boost. They are polyclonal and polyvalent in the sense that they are reactive with both HA and NA envelope antigens of the virus. Those made to viral HA/NA antigenic hybrids can be used as HA or NA-specific reagents when immunization has been carried out with antigenically hybrid reassortant viruses in which either the HA or NA antigen is alien to human experience and therefore not significantly cross-reactive in tests in which response to one or the other antigens is measured in subjects previously primed to both by natural infection or vaccination.