Long-term response to vaccination against pneumococcal antigens in kidney transplant recipients

We have recently shown that kidney transplant recipients with clinically stable condition can produce almost normal antibody concentrations at month 1 after vaccination against Streptococcus pneumoniae. It was the aim of the present study to define the long-term efficacy of this vaccination in a similar cohort.

Using Pneumovax 23, we immunized 49 kidney transplant recipients (21 women and 28 men, aged 29-74 years). Antibodies against 14 pneumococcal serotypes were determined before vaccination and at months 1 and 15 after vaccination by Luminex assay.

The total antibody concentration (median [range]) increased from 18.2 mg/L (2.9-55.5 mg/L) before vaccination to 53.6 mg/L (4.5-132.4 mg/L) at month 1 and 41.3 mg/L (4.9-105.0 mg/L) at month 15 (P<0.0001 as compared with before vaccination). The antibody concentration at month 15 was 77% of the response at month 1. The number of pneumococcal serotypes recognized was 8 (0-13) before vaccination, 13 (0-14) at month 1, and 11 (0-14) at month 15. At month 15, the total antibody concentration and the number of serotypes with protective antibodies already displayed a significant decrease (P<0.0001 each) as compared with month 1. It could be shown that the decrease in antibody concentrations (months 1-15) was minor in younger patients, in women, in patients receiving cyclosporine A versus tacrolimus, and in patients with better kidney function.

Our results demonstrate that, at month 15 after vaccination versus before vaccination, kidney transplant recipients with clinically stable condition still display higher antibody concentrations against pneumococci. Therefore, they should be partly protected against pneumococcal infection until month 15.