Abstract
A limited assessment of immunity to diphtheria revealed that only 44.8% of adults had protective levels (greater than 0.01 U/ml) of diphtheria antitoxin in their sera. In the light of this information, it was decided to assess the suitability of Adult-type Tetanus-Diphtheria Vaccine as a replacement for Adsorbed Tetanus Vaccine in occupational health schemes. A comparative study of these vaccines showed that a single dose of each produced an equivalent rate and level of tetanus antitoxin responses. Adult-type Td Vaccine elicited more than fourfold increases of diphtheria antitoxin in 76% of vaccinees. No statistically significant differences were observed in the clinical reactivity of the vaccines under test. However, the combined vaccine caused a slightly higher incidence of local reactions (pain, redness and swelling) while recipients of Adsorbed Tetanus Vaccine more frequently experienced pain.