Impaired Antibody Responses to Pneumococcal Polysaccharide in Elderly Patients with Low Serum Vitamin B12 Levels

Objective : To determine whether immunocompetent elderly patients with low serum vitamin B 12 levels have impaired serum antibody responses to the 23-polyvalent pneumococcal polysaccharide vaccine. Design : Controlled, prospective cohort study. Measurements : 15 patients with low serum vitamin B 12 levels and 15 age- and diagnosis-matched patients with normal levels were vaccinated. Serum antibody titers to 12 pneumococcal serotypes were measured by radioimmunoassay before and 4 weeks after vaccination. Results : The difference between the geometric mean of the vaccine antibody titers before and after vaccination for all 12 serotypes was lower (P = 0.005) in the patients with low vitamin B 12 levels than in the patients with normal levels. When mean corpuscular volume and age were controlled for, vitamin B 12 remained an independent predictor of antibody response (P = 0.005). Erythrocyte mean corpuscular volume was also an independent predictor of the increase in titer (P = 0.03). Conclusions : Patients with low vitamin B 12 levels had impaired antibody responses to pneumococcal vaccine. Further study is necessary to determine whether treatment with vitamin B 12 can enhance specific immunoglobulin synthesis and improve the clinical efficacy of the pneumococcal vaccine in patients with low vitamin B 12 levels.