Assessment of delayed skin sensitivity induced by freeze-dried Japanese percutaneous BCG vaccine

Abstract

Percutaneous BCG vaccination with the freeze-dried Glaxo percutaneous vaccine has been practised in South Africa for some years. In an investigation conducted in the Transvaal region in 1971 it was found that the BCG-induced delayed skin sensitivity (allergy) was very low. After the introduction of the freeze-dried Japanese percutaneous vaccine for routine vaccination in 1973, the allergy induced by this vaccine was assessed in a controlled study on 1 900 Black schoolchildren. They were tested with the Mantoux and Heaf methods simultaneously and the negative reactors* were vaccinated with the freeze-dried Japanese percutaneous vaccine. One-tenth of the children eligible for vaccination were left unvaccinated to serve as a control group. Ten to twelve weeks after vaccination the immune response was assessed by simultaneous testing with Mantoux and Heaf. For the Mantoux test three different strengths of tuberculin were used in different groups: 2 TU, 5 TU, and 10 TU of PPD RT 23 with Tween, respectively. The freeze-dried Japanese percutaneous BCG vaccine induced a satisfactory, and in a substantial proportion a high level of allergy in the vaccinated children, as measured in terms of mean induration, of increase of mean induration, and 'conversion rate'. The allergic response was commensurate with the test dose used: the stronger the test applied, the larger the reactions elicited by it. The allergy induced by this vaccine was significantly higher than that induced by the freeze-dried Glaxo percutaneous vaccine used previously.

S. Afr. Med. J., 48, 2187 (1974).