[Studies on the oral administration of live attenuated poliovirus vaccine in the monkey].

The live attenuated poliovirus vaccine of Cox was administered in monkeys and clinical, virological and histological studies conducted. The trivalent vaccine and a mixture of the 3 monovalent vaccines were used. Clinical symptoms suggestive of poliomyelitis were not observed in any of the animals. The stcol, blood and spinal fluid were examined for virus following administration of vaccine. A mixture, Type I or Type II virus was isolated from the stool of all except one animal. Virus could not be isolated from the blood, or spinal fluid or from tissues obtained on dissection of the animals. Histological examination of the tissues revealed no significant changes in the cerebrum or cerebellum but in the spinal cord, there was a decrease in number, degeneration and phagocytosis of neurons in the anterior horn, especially the cervical and lumbar cord. Compared to the changes in typical poliomyelitis, the findings were slight but in contrast to the control the changes were definite. Infiltration by inflammatory cells was observed in the mucous tissue of the small and large intestines and sinuitis was found in the mesenterial lymphnodes. The findings suggest that proliferation of virus takes place at this site. The results suggest that administration of the Cox vaccine in the form of a mixture of the 3 types may be accompanied by some danger. The reason for this is that the attenuated virue still possesses some neurotropicity and also due to the administration of the 3 types of virus at the same time.