[Meningoencephalitis after vaccination against yellow fever with the 17 D strain: 2 cases]

The authors report two cases of meningoencephalitis consecutive to immunization with the 17 D yellow fever virus in adults. This complication is exceptional; the rare cases previously reported usually occurred in children. The meningoencephalitis had no particular clinical features; it was more severe in our second case but nevertheless followed a favourable course, as usually described in the literature. The pathogenesis of these central nervous system reactions is unclear. In our two cases the vaccine seems to have acted synergistically with another neurotropic virus (adenovirus in the first case, unknown virus in the second) which was either pre-existing and latent or occurring de novo.