Revaccination of Adults Against Diphtheria I: Responses and Reactions to Different Doses of Diphtheria Toxoid in 30–70‐year‐old Persons With Low Serum Antitoxin Levels

Abstract

Heron, I. Revaccination of adults against diphtheria toxoid in 30-70-year-old persons with low serum antitoxin levels. Acta path. microbiol. immunol. scand. Sect. C . 94: 2 13-2 18, 1986.Studies of diphtheria antitoxin levels in serum from adult populations have indicated high frequencies of unprotected subjects. Serum from 351 randomly selected Danes between 30 and 70 years old has been assessed for antitoxin concentration; 123 persons among these, who had low antibody levels, received one vaccination with 2 Lf. 5 Lf or 12 Lf diphtheria toxoid. Side-reactions were recorded, and antibody levels were studied 4 weeks later. Antitoxin concentration following vaccination increased markedly to above protective level in 83% of those vaccinated. Of subjects, who could document a complete primary vaccination series, only one receiving 2 Lf 3 1 years after primary vaccination did not attain protective antitoxin level. Minor local reactions only were recorded among subjects who did not respond serologically to vaccination. Frequencies of more pronounced reactions experienced by serologically responding subjects depended on dose and were 15%, 14% and 23% respectively. It was concluded that a single vaccination of the present adult Danish population will induce protective antibody levels so frequently that the effect of herd immunity will secure against epidemics if future diphtheria outbreaks are experienced. To secure individual protection, vaccination history and/or serological assessments have to be explored in order to decide whether a single vaccination is sufficient.

Revaccination of Adults Against Diphtheria Ii: Combined Diphtheria and Tetanus Revaccination With Different Doses of Diphtheria Toxoid 20 Years After Primary Vaccination

“…In the present work we wanted to study antibody response and side-reactions following revaccination, without prevaccination immunity tests, in an adult population, to gain information of importance for possible future mass vaccination programs. As discussed in the accompanying paper (14), an increasing risk of diphtheria outbreaks may be foreseen since immunity after childhood vaccination is temporary and relative high frequencies of nonprotection are observed among adults.…”

“…Results from this technique correspond to results obtained by in vivo neutralization assay in rabbits and guinea-pigs. An antibody content in serum of 0.01 IU/ml is generally accepted to be the minimal protective level (14).…”

“…Outbreaks ofdiphtheria in countries where diphtheria was thought to be nearly eradicated has provoked a particular interest in the effect of and side reactions to diphtheria revaccination of adults ( 14). It is well known that adults more frequently suffer side-reactions to diphtheria vaccination than do children (9,18).…”

“…For primary vaccination of adults, smaller doses of diphtheria toxoid, compared to vaccines for pediatric use, are generally recommended. For revaccination against diphtheria in childhood, even a 2 Lf(F'loccu1ation units) dose has been found sufficient to induce long-term immunity (1 6), but 2 Lf has been found not to secure protection in any case following revaccination of adults primary vaFcinated more than 20 years earlier (14). However, the aim of complete protection should be counter-balanced against the side-reactions, which increase with increasing toxoid dose.…”

“…The dose-reaction relationship was initially investigated in adults with low serum antitoxin levels, as reported in the preceding paper (14). Reactions to 12 Lf recommended for primary vaccination of adults were found to be significantly more promi-nent compared, to those of lower doses.…”