# Long-term persistence of pneumococcal antibodies 5 years after a sequential PCV13 and PPSV23 vaccination in kidney transplant recipients: indications for revaccination

## TL;DR

This study shows that pneumococcal antibodies in kidney transplant recipients remain elevated for up to 5 years after sequential vaccination, suggesting a booster may be beneficial.

## Contribution

The study provides the longest longitudinal data on antibody persistence after sequential PCV13 and PPSV23 vaccination in kidney transplant recipients.

## Key findings

- Five years after vaccination, antibody concentrations remained above baseline in most participants.
- Mean IgG levels were threefold higher than pre-vaccination values.
- Serotype-specific responses showed minimal decline but remained lower than in healthy individuals.

## Abstract

Pneumococcal vaccination is essential to prevent invasive Streptococcus pneumoniae infections in immunocompromised individuals, including kidney transplant recipients. Current recommendations favor single-dose immunization with higher-valent conjugate vaccines, including PCV20 or PCV21. Five years ago, sequential administration of the 13-valent conjugate vaccine (PCV13) followed by the 23-valent polysaccharide vaccine (PPSV23) represented standard of care. Long-term data on antibody persistence after this regimen remain limited. In this prospective 5-year follow-up study, 46 kidney transplant recipients previously vaccinated sequentially with PCV13 and PPSV23 were re-evaluated. Nine patients were lost to follow-up, and 11 had died during the observation period. The remaining 26 participants were re-enrolled and completed the 5-year assessment. Global and serotype-specific IgG anti-pneumococcal antibody concentrations were quantified and compared with baseline and 12-month post-vaccination levels. Clinical outcomes, including pneumococcal infections and allograft status, were recorded. Five years after vaccination, antibody concentrations remained above baseline levels in most participants. Mean IgG levels were still approximately threefold higher than pre-vaccination values. Even for serotype-specific responses, mean antibody levels showed minimal changes compared with those measured 12 months after the first vaccination, although absolute titers remained considerably lower than those observed in healthy individuals. No cases of pneumococcal pneumonia or vaccine-associated allograft rejection occurred during follow-up. Sequential vaccination elicits durable immune responses in kidney transplant recipients, persisting up to 5 years post-immunization. With the availability of new vaccines covering additional serotypes, and given the generally lower antibody responses in this high-risk population, a booster with PCV20 or PCV21 appears advisable to enhance and broaden protection.

Kidney transplant recipients are at high risk for invasive pneumococcal disease, yet long-term vaccine-induced immunity in this population remains poorly defined. This study provides one of the longest longitudinal assessments of humoral responses following sequential PCV13 and PPSV23 vaccination, extending to 5 years post-immunization. We demonstrate sustained but heterogeneous antibody persistence and serotype-dependent responses to PCV20 booster vaccination. These results are directly relevant to transplant clinicians, vaccinologists, and public health policy, offering critical insight into long-term pneumococcal immunity in immunocompromised hosts and guiding future vaccine scheduling in solid organ transplantation.