BOOSTER DIPHTHERIA IMMUNIZATION IN ADULTS

Background and objective: Nearly 50% of adults in Germany have no meas urable antibody protection against diphtheria, even though most of the m will have been vaccinated against it in their childhood. We investig ated how vaccination should be performed in this situation to provide lasting protection. Material and Methods: 100 adults (53 men, 47 women ; mean age 27.7 [19-54] years) whose last diphtheria Vaccination had b een at least 10 years previously, were injected up to three times with customary commercial monovalent diphtheria vaccine for adults (5 IU t oxoid/0.5 ml), at intervals of 4-8 weeks. Each time, before and 4-8 we eks after the latest injection, the antitoxin level was determined by cell-culture neutralization test. Results: Before the vaccination 30 o f the 100 subjects had protection against diphtheria (antitoxin level >0.1 IU/ml), 24 had ''basic immunity'' (0.01 to <0.1 IU/ml), and 46 no measurable protection (<0.01 IU/ml). After the first booster the prot ection threshold had not been reached in seven of the 100, all of them women. The main determinant for the pre- and post-vaccination antitox in level was the interval since the last vaccination. In addition, wom en had significantly lower pre- and postvaccination levels than men. B ut after the second and third booster the antitoxin level of the seven women had risen to above the protection threshold, while the geometri c mean of the whole collective had fallen, despite further boosters. I t was 0.015 IU/ml before vaccination, 1.156 IU/ml after the first boos ter, 0.924 IU/ml after the second, and 0.952 after the third. Conclusi on: Those adults who were last vaccinated against diphtheria more than 20 years ago should have two booster shots, more than 8 weeks apart, so that the highest possible and most lasting antitoxin level can be a chieved. Women in particular should have at least two booster shots, a s their antitoxin response tends to be less than that of men.