YELLOW-FEVER 17D VACCINE VIRUS ISOLATED FROM HEALTHY VACCINEES ACCUMULATES VERY FEW MUTATIONS

The live attenuated yellow fever (YF) vaccine strain 17D is one of the safest vaccines in use today with only 22 cases of reversion to virul ence documented from over 300 million doses administered. We have isol ated virus in cell culture from sera of six volunteers who received 17 D vaccine and found that very few nucleotide mutations were detected i n the consensus sequence of the entire genome of each of the serum vir uses. Moreover, most of these mutations accumulated in the non-structu ral protein genes, especially the NS5 protein gene. Although no nucleo tide change was identified in the structural protein genes of any of t hese six serum viruses, minor sequence heterogeneity existed in the se rum virus population. Our results indicate that 17D vaccine virus accu mulates mutations at a very low frequency and may explain in part the excellent safety record of 17D vaccine. (C) 1998 Elsevier Science B.V. All rights reserved.