49 Det aktive stof i vaccinen er Gul feber- virus, af stammen 17 D- 204 (dyrket i hønseæg), som er levende, men er blevet svækket således at den ikke forårsager gul feber hos raske personer.
The active ingredient in the vaccine is Yellow fever virus of the 17 D-204 strain (grown in hens eggs) that is live but has been weakened so that it does not cause yellow fever in healthy persons.