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Assessing the Immunogenic Response of a Single Center's Pneumococcal Vaccination Protocol in Sickle Cell Disease
Jonathan D Santoro1, Leann Myers, Julie Kanter
1*Department of Neurology, Stanford University School of Medicine, Stanford, CA †Department of Biostatistics, Tulane University School of Public Health and Tropical Medicine, New Orleans, LA ‡Department of Pediatric Hematology-Oncology, Medical University of South Carolina, Charleston, SC.
Insights
Patients with sickle cell disease (SCD) often lack protective pneumococcal antibody levels years after vaccination. This study suggests current vaccination schedules may not adequately protect SCD patients from invasive pneumococcal disease.
Area of Science:
- Hematology
- Immunology
- Pediatrics
Background:
- Sickle cell disease (SCD) patients face a high risk of invasive pneumococcal disease.
- Penicillin prophylaxis and pneumococcal vaccination are crucial for infection prevention in SCD.
- Optimal pneumococcal vaccination schedules for SCD patients remain undefined.
Purpose of the Study:
- To evaluate the immunogenicity of a specific pneumococcal vaccination strategy in pediatric SCD patients.
- To assess antibody titers following sequential Prevnar (PCV-7) and Pneumovax (PPV-23) vaccination.
- To determine if the current vaccination regimen maintains protective antibody levels over time.
Main Methods:
- Multiplex bead analysis was used to measure antipneumococcal antibody titers.
- The study assessed patients vaccinated with PCV-7 followed by PPV-23 at ages 2 and 5, with subsequent PPV-23 every 5 years.
- Immunogenicity was evaluated in a cohort of pediatric patients with SCD.
Main Results:
- A significant proportion of SCD patients did not maintain sufficient antipneumococcal antibody response to PPV-23 for 5 years.
- Only 36% of patients had protective antibody titers at a mean of 37 months post-vaccination.
- Among those with subtherapeutic titers, 64% responded to less than 25% of tested serotypes, with response decline occurring earlier than previously reported.
Conclusions:
- The current pneumococcal vaccination strategy may not optimally maintain antipneumococcal immunity in SCD patients.
- Findings indicate vulnerability to invasive pneumococcal disease, especially as prophylactic penicillin is often discontinued at age 5.
- Further research is recommended for optimal vaccine schedules and titer monitoring in at-risk SCD populations.
Abstract:
Sickle cell disease (SCD) is the most common inherited hematologic disorder in the United States. Patients with SCD are at increased risk of invasive pneumococcal disease and are reliant on both early penicillin prophylaxis and antipneumococcal vaccination for prevention of infection. Although studies examining vaccine response have demonstrated a drop-off of titer response after 3 years, an optimal vaccination regimen has not been identified. Our study sought to assess the immunogenicity of our center's pneumococcal vaccination strategy, which included Prevnar (PCV-7) (before the introduction of PCV-13) followed by Pneumovax (PPV-23) given routinely at 2 and 5 years of age and then every 5 years thereafter. Our goal was to assess vaccine response in a population of patients with SCD who had received vaccines according to this regimen using multiplex bead analysis. Our study demonstrated a significant percentage of persons with SCD do not maintain a sufficient vaccination response to PPV-23 for 5 years. Our study revealed that only 36% of patients had protective levels of antipneumococcal antibody titers at an average of 37 months after vaccination. Most alarmingly, within the group of patients with subtherapeutic titers, 64% demonstrated vaccine response to <25% of the tested serotypes. These findings were significantly associated with duration of time since last vaccine administration, but the mean age of lack of response was below the 3-year window where vaccine response was previously reported to wane. Our results indicate antipneumococcal immunity may not be optimally maintained using this vaccination strategy in patients with SCD leaving them vulnerable to invasive pneumococcal disease. Many pediatric hematologists stop prophylactic penicillin at 5 years of age making these results alarming. We recommend further investigation into an optimal vaccine schedule and monitoring of antipneumococcal titers in at-risk patients.
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