Serotype specific pneumococcal vaccine effectiveness in children with sickle cell disease: A two-decade analysis

Abstract

Objectives: Sickle cell disease (SCD) is the most common genetic hematologic disease globally and children with SCD are at increased risk for pneumococcal disease. Methods: We utilized data from population-based enhanced surveillance for invasive pneumococcal disease (IPD) in children <18 years of age in Massachusetts from 2002 to 2020. We calculated incidence rates (IR) among children with SCD using bootstrapping resampling and incidence rate ratios (IRR) for pre- and post-PCV13 periods. Vaccine effectiveness (VE) was calculated as 100*(1-IRR), and PCV13 vaccine failure probability was predicted using a random forest model. Results: Children with SCD had higher IR during both pre−/post-PCV13 periods compared with otherwise healthy children 240.0/100,000 versus 4.6/100,000 in pre-PCV13 period (2002–2009); 172.7/100,000 versus 1.9/100,000 in post-PCV13 period (2011−2020), respectively. After widespread use of PCV7 for a decade, a modest reduction of 28.1 % (95% CI 25.9–37.2%) in the incidence of overall IPD during the post-PCV13 period was observed in children with SCD, whereas a more substantial 59.5% (96% CI 57.8–61.4%) reduction was observed in otherwise healthy children. There was a 60.8% (95% CI 55.2%-NA) reduction in the incidence of VST13 IPD in children with SCD and an 83.0% (95% CI 80.67–85.63%) reduction in children without underlying health condition. Overall, 61.1% of the remaining IPD among children with SCD were due to non-PCV13 serotypes (8, 10A, 15A,15B, 22F, 23B), many of which are included in expanded valency vaccines. Conclusion: Children with SCD continue to have higher rates of IPD compared with otherwise healthy children despite vaccination. Majority of the remaining disease is due to serotypes not included in vaccine formulations that have been used for the last two decades. Our study highlights the potential value of expanded valency vaccines and importance of risk-based vaccination strategies tailored for this vulnerable population.