An allergen-free antirabies vaccine.

Studies on the development of encephalitogenic activity in the cerebral tissue of various animals (rabbits, rats, mice and sheep) showed that the brains of albino rats did not become encephalitogenic until after the 18th day of life, which is later than in any of the other animals studied. On the basis of this finding, a method was developed for the preparation of an entirely allergen-free, non-encephalitogenic antirabies vaccine using the brains of suckling rats. The phenolized vaccine, both in liquid and in lyophilized form, consistently gave high antigenic titres when tested in animals and produced a good increase in virus-neutralizing antibodies in man. It also showed a low thromboplastic activity. More than 1500 litres of this vaccine have since been manufactured on an industrial scale and more than 9500 persons vaccinated. General reactions have been far less frequent than with the conventional Fermi vaccine and no neuroparalytic accidents or shock reactions have been reported. Vaccination with the allergen-free vaccine has proceeded smoothly even in persons considered to be especially at risk owing to previous vaccination with antirabies vaccine or a history of trauma or disease of the central nervous system.