University officials say the tularemia vaccine researchers thought they were working with a harmless "vaccine strain" of the Francisella tularensis bacterium.

Pestivirus vaccines exist and the correct vaccine strain should be given, depending on the herd's location and the endemic strain in that region.

The reason for this, ironically, is that the group used the vaccine strain of the bacterium.

These vaccine strains are missing the genes that cause a symptomatic response.

The experiment involved inserting toxin-making genes from a closely related and usually harmless microbe, Bacillus cereus, into the Russian vaccine strain.

Looking at the past phylogenetic relationships of the influenza virus can help lead to information regarding treatment resistance, selecting vaccine strains, and future influenza strains.

As the disease is not endemic in the EU, the selection of the appropriate vaccine strain would be a pure lottery.

By the seventh passage, the vaccine strains could no longer infect nervous tissue or cause paralysis.

The remaining 397 viruses belong to the B/Victoria lineage and are not related to the vaccine strain.

Low-attenuated vaccine strains may cause damage to the bursa of Fabricius and immunosuppression in susceptible chicks.