[Diphtheria antitoxin level 2 years after booster vaccination]

Area of Science:

• Immunology
• Vaccinology
• Public Health

Background:

• Diphtheria remains a public health concern, necessitating robust immunity in adult populations.
• Assessing the long-term immunogenicity of diphtheria booster vaccinations is crucial for maintaining herd immunity.
• Previous diphtheria vaccination status significantly impacts current antitoxin levels.

Purpose of the Study:

• To compare the immunogenicity of single versus dual diphtheria booster vaccinations.
• To evaluate both short-term and long-term immune responses to diphtheria boosters.
• To determine optimal booster strategies for adults with waning immunity.

Main Methods:

• Prospective, controlled, randomized, multicenter study design.
• Inclusion of subjects whose last diphtheria vaccination was over 10 years prior.
• Assessment of diphtheria antitoxin levels at multiple time points post-vaccination (4 weeks, 1 year, 2 years).

Main Results:

• A single diphtheria booster vaccination significantly reduced the percentage of unprotected subjects from 27% to 5%.
• A second booster vaccination showed a limited additional benefit, with only one of five initially unprotected subjects achieving protective levels.
• Long-term follow-up revealed sustained, albeit reduced, protection, with 7-8% of subjects remaining below protective antitoxin levels at 1 and 2 years.

Conclusions:

• A single diphtheria booster vaccination is highly effective in restoring protective immunity in adults.
• A second diphtheria booster vaccination offers minimal serological advantage when administered four weeks after the first.
• Current diphtheria booster vaccination schedules may require re-evaluation for long-term efficacy in adult populations.