Abstract: A rabies vaccine composition is disclosed which comprises a sterilized suspension of proteineous suckling mice or rat brain particles of injectable particle size laden with an amount of inactivated rabies virus which is equivalent to a virus titer of from at least about 10.sup.5 to about 10.sup.7 MLD.sub.50 per 0.01 milliliter thereof at a brain tissue concentration of from about 3 to about 6% by weight, in an aqueous buffer solution having a pH of between about 7.5 and about 8.4, and comprising an amount, dissolved therein, of between 0.03 and 0.08 moles per liter of a buffer composition comprising a mixture of an organic base of the formula ##STR1## wherein R.sub.1 and R.sub.2 each are hydrogen or CH.sub.2 CH.sub.2 OH and an acid addition salt thereof, preferably a mixture of tris (hydroxymethyl)amino methane and its hydrochloride. The vaccine composition exhibits a high potency and its pH value remains stable over a prolonged period of time.