Vaccine Immunity Against Pneumococcus in Children With Sickle Cell Disease: A Retrospective Single-center Study

Sickle cell disease (SCD) patients are at a higher risk of pneumococcal invasive diseases. Vaccination is the central strategy for protecting these children, along with penicillin prophylaxis. However, it is unclear how often these children should be revaccinated with pneumococcal vaccines. This retrospective study aimed to describe the pneumococcal vaccination status of children with SCD in a high-income country with access to vaccines, to see if the national vaccination guidelines are followed and effective at inducing good vaccine seroprotection. We also wanted to assess the longitudinal vaccine immunity and the effect of booster doses on vaccine seroprotection.

Electronic medical records of 42 children with SCD diagnosed between 2009 and 2023 were retrospectively reviewed. Clinical demographic data and pneumococcal serologies were analyzed.

Of the 42 patients included in the study, 34 (81%) had available vaccine records. All of these patients had completed the age-appropriate vaccination schedule. Among them, 15 (44%) had received at least 1 booster dose, with a mean age of 3.47 years at the time of the booster. A Kaplan-Meier analysis revealed a significant decline in seroprotection after the age of 5 years following completion of the vaccination series.

Our findings suggest that a booster vaccination may be necessary 5 years after the completion of the primary pneumococcal vaccination series. Further large-scale prospective studies are required to better define the optimal frequency of booster doses throughout life and to identify individual factors that contribute to the loss of serological protection.