Long-term persistence of antibodies after diphtheria/tetanus vaccination in immunosuppressed patients with inflammatory rheumatic diseases and healthy controls

Many vaccines demonstrate high effectiveness for years. This prospective multicentre study was conducted in Switzerland to assess the long-term persistence of antibodies to the diphtheria/tetanus (dT)-vaccine in adult patients with rheumatic diseases (PRDs). 163 PRDs and 169 controls were included in the study. The median age of all participants was 50 years (range: 18-83 years) and 56% were female. After a median time interval of 16 years after vaccination, the median anti-vaccine antibody concentrations were lower in PRDs than in controls for tetanus (1.68 vs 2.01; p = 0.049) and diphtheria (0.05 vs 0.22; p = 0.002). Based on the currently accepted seroprotection threshold (antibody concentration ≥ 0.1 IU/ml), PRDs had lower proportions of short-term tetanus and diphtheria protection as demonstrated by crude odds ratios (OR) of 0.30 (p = 0.017) and OR: 0.52 (p = 0.004), respectively. After adjusting for 'age' and 'time since last dT vaccination', the strength of associations became weaker; for tetanus, borderline evidence remained for a true difference between PRDs and controls (OR: 0.36 [p = 0.098]), however, not for diphtheria (OR: 0.86 [p = 0.58]). We hypothesize that in the presence of rheumatic diseases and its immunosuppressive treatment, vaccine-specific long-lived plasma cells (LLPCs) may be diminished or competitively displaced by rheumatism-specific LLPCs, a process which may decrease the persistence of vaccine-specific antibodies. Novel studies should be designed by incorporating methodologies allowing to determine the attributable fraction of immunosuppressive/immunomodulatory medications and rheumatic disease itself on long-lasting vaccine-specific antibody persistence, as well as, further study the role of LLPCs.