Purpose <p>In patients with SARS-CoV-2 infection overweight and diabetes are associated with poor prognosis. Therefore, effectiveness and tolerance of booster vaccination against SARS-CoV-2 has to be ensured. We examined the impact of overweight and diabetes on anti-SARS-CoV-2-titers and the incidence of side effects after booster vaccination.</p> Methods <p>We performed a cross-sectional study with consecutive recruitment and convenience sampling of 100 participants vaccinated three times against SARS-CoV-2. Anti-SARS-CoV-2-titers, immunological parameters and biochemical markers of glucose metabolism were measured. Prevalence of vaccination side effects was assessed by personal interview. Moreover, metabolic status was assessed by performance of body composition measurement and body impedance analysis. The glycemic and metabolic parameters were correlated with the anti-SARS-CoV-2-titers and the incidence of side effects. The results were compared between patient with and without overweight and diabetes.</p> Results <p>Levels of anti-SARS-CoV-2-titers did not differ between participants with and without overweight (5756.6 ± 6848.9 vs. 4997.0 ± 5050.3, p.83) or participants with and without diabetes (6681.0 ± 6795.2 vs. 5124.0 ± 5070.4 BAU/ml, <i>p</i> = .28). Moreover, the investigated glycemic parameters and parameters of the body composition measurement and body impedance analysis did not present any correlation with the antibody levels. Furthermore, we could reveal that vaccination side effects are more likely to occur in participants without diabetes (OR 2.9 (95%-CI: 0.5–4.3, p.04)).</p> Conclusions <p>Overweight and diabetes are not associated with lower anti-SARS-CoV-2-titers after booster vaccination. Parameters of the body composition and body impedance analysis did not reveal any further association regarding development of anti-SARS-CoV-2-titers. Vaccination side effects are more likely to occur in participants without diabetes.</p>