Is there an alternative to the 17D amaril vaccine?

The live attenuated yellow fever vaccine 17D was found as early as 1936 by M. THEILER Of the Rock-feller Foundation. This strain of yellow fever is st ill the only one used today. The experience acquired with this vaccine has led to various changes in its composition: - use of the seed lot system (in 1941) following the accidents observed in Brazil ; - elimination of human plasma as stabilising agent because of hepatitis B t ransmission (1942) ; - preparation of a vaccine free of avian leukemia ; - perfection of a thermostable vaccine (1984). These various successive improvements resulted in one of the most effective vaccines. Over the past years, different ways of improving the vaccine have been envi saged: change of cellular substrate purifications, development of a new vac cine through genetical engineering. We will review these different approach es in order to gauge their advantages and drawbacks both from a legislative and pharmaceutical point of view. It has been recently suggested that an infected cDNA clone from the 17D str ain be used as a yellow fever vaccine or as a gene-vector for other flavivi ruses. This most promising approach raises questions, notably ones of secur ity and legislation which we will discuss.