Fig. 1From: The Double-Edged Sword: How Evolution Can Make or Break a Live-Attenuated Virus Vaccinea The Pastorian approach for attenuation by serial passage b Passage history of three live-attenuated virus vaccines derived by serial passage: the yellow fever virus 17D vaccine strain (Monath et al. 2008), the cold-adapted influenza A/Ann Arbor/6/60 vaccine strain (Maassab and DeBorde 1985), and the chickenpox (varicella) Oka vaccine strain (Hambleton and Gershon 2005; Takahashi et al. 2008)Back to article page