This is a clinical study conducted with a view to determining the effect of Vitamin A on the prevention of Ascaris re-infection. 692 school children were used as subjects of study. A strict preliminary examination was conducted from February to October, 1957, as a result of which 110 children were deliberately selected. Such 110 children were divided into two groups at random, one of which was given V. A.(10, 000 IU per capita daily) for a whole year, and the other served as a control group. Thus, during the period of V. A. administration and during the 9 months' follow-up period succeeding it, the occurrence of re-infection was closely observed for comparative study.
A. Preliminary examination
1) The cumulative rate of re-infection among school children during 6 months' time was 42.0%. 2) All the egg-positive children were subjected to mass anthelmintic treatment in February and in June. And, from among those whose conversion to negative was confirmed by the August stool examination, but who had previously been positive both in May and in June and also positive from February to April consecutively or who had become negative as a result of treament executed in February but had been infected again thereafter, 110 children were finally chosen at random for the purpose of this experiment. These 110 persons were divided at random into two groups;then it came out that they were of practically holomogous composition as to the sex distribution ratio and the severity of infection (number of eggs detected). 3) For caution's sake, these subjects were again given two courses of anthelmintic treatment before the experimental administration of V. A, i. e. in September and in October, so that the possible inclusion of such cases as those who had larvae circulating within one or other organ unnoticed or of false negative cases be eliminated.
B. Results of experimental V. A. administration and follow-up results
1) Re-infection rate during the period of V. A. administration: The rate of the V. A. administered group was markedly lower than that of the control group. 2) Transition of the cumulative re-infection rate: After 5 months of the commencement of the V. A. administration, marked difference was observed in the ascending rates of the two groups. At the termination of the V. A. admintration, the V. A. administered group showed 29.1% while the control group reached to 60.0%-significant difference was obtained between the two values. 3) Relationship between the severity of infection prior to treatment and the severity of re-infection that took place during the V. A. administration: No definite relationship was recognized. 4) Severer re-infection occurred more frequently in the control group. 5) Spontaneous conversion to negative during the V. A. administration period: No significant difference was seen between the two groups. 6) Transition of the cumulative rate of re-infection during the follow-up period: The two groups presented no particular difference. Rise of the re-infection rate in V. A. administered group was ascribed to the lack of long lasting effect of V. A. 7) No side effect was recognized in the administration of V. A.
It is concluded that V. A. is effective in preventing round-worm re-infection, but its effect appeared not long lasting.
