Carbon Source-Dependent Changes of the Structure of Streptococcus pneumoniae Capsular Polysaccharide with Serotype 6F

Cost-Effectiveness Analysis of the Use of V116, a 21-Valent Pneumococcal Conjugate Vaccine, in Vaccine-Naïve Adults Aged ≥ 65 Years in the United States

INTRODUCTION

Given the recent approval and recommendation of V116, a 21-valent pneumococcal conjugate vaccine (PCV), in the United States (US), we evaluated the cost-effectiveness of using V116 versus the 20-valent PCV (PCV20) or the 15-valent PCV (PCV15) in series with the 23-valent pneumococcal polysaccharide vaccine (PPSV23) among adults aged ≥ 65 years in the US who had never received a PCV previously.

METHODS

A static multi-cohort state-transition Markov model was developed to estimate the lifetime incremental clinical and economic impact of V116 vs. PCV20 or PCV15 + PPSV23 from the societal perspective. All model inputs were based on published literature and publicly available databases and/or reports. Model outcomes included undiscounted clinical cases: invasive pneumococcal disease (IPD), inpatient and outpatient non-bacteremic pneumococcal pneumonia (NBPP), post-meningitis sequelae (PMS), deaths from IPD and inpatient NBPP, discounted quality-adjusted life years (QALYs) as well as the discounted total cost (in 2023 USD), which consisted of vaccine acquisition and administration costs, direct and indirect costs associated with the disease, and travel costs for vaccination. The final summary measure was the incremental cost-effectiveness ratio (ICER), reported as $/QALY gained. Three percent was used for the annual discounting rate.

RESULTS

Based on the inputs and assumptions used, the results indicated that the V116 strategy prevented 27,766 and 32,387 disease cases/deaths and saved $239 million and $1.8 billion in total costs when compared to the PCV20 and PCV15 + PPSV23 strategies, respectively, in vaccine-naïve adults aged ≥ 65 years. The estimated ICERs were cost saving in both regimens (i.e., V116 vs. PCV20 or vs. PCV15 + PPSV23). The scenario analysis and deterministic and probabilistic sensitivity analyses also demonstrated the robustness of the qualitative results.

CONCLUSIONS

These results demonstrated that using V116 in adults aged ≥ 65 years in the US can prevent a substantial number of PD cases and deaths while remaining highly favorable economically over a wide range of inputs and scenarios.

Pneumococcal Vaccine for Adults Aged ≥19 Years: Recommendations of the Advisory Committee on Immunization Practices, United States, 2023

This report compiles and summarizes all published recommendations from CDC’s Advisory Committee on Immunization Practices (ACIP) for use of pneumococcal vaccines in adults aged ≥19 years in the United States. This report also includes updated and new clinical guidance for implementation from CDC

Before 2021, ACIP recommended 23-valent pneumococcal polysaccharide vaccine (PPSV23) alone (up to 2 doses), or both a single dose of 13-valent pneumococcal conjugate vaccine (PCV13) in combination with 1–3 doses of PPSV23 in series (PCV13 followed by PPSV23), for use in U.S. adults depending on age and underlying risk for pneumococcal disease. In 2021, two new pneumococcal conjugate vaccines (PCVs), a 15-valent and a 20-valent PCV (PCV15 and PCV20), were licensed for use in U.S. adults aged ≥18 years by the Food and Drug Administration

ACIP recommendations specify the use of either PCV20 alone or PCV15 in series with PPSV23 for all adults aged ≥65 years and for adults aged 19–64 years with certain underlying medical conditions or other risk factors who have not received a PCV or whose vaccination history is unknown. In addition, ACIP recommends use of either a single dose of PCV20 or ≥1 dose of PPSV23 for adults who have started their pneumococcal vaccine series with PCV13 but have not received all recommended PPSV23 doses. Shared clinical decision-making is recommended regarding use of a supplemental PCV20 dose for adults aged ≥65 years who have completed their recommended vaccine series with both PCV13 and PPSV23

Updated and new clinical guidance for implementation from CDC includes the recommendation for use of PCV15 or PCV20 for adults who have received PPSV23 but have not received any PCV dose. The report also includes clinical guidance for adults who have received 7-valent PCV (PCV7) only and adults who are hematopoietic stem cell transplant recipients

Anatomical site-specific carbohydrate availability impacts Streptococcus pneumoniae virulence and fitness during colonization and disease

Streptococcus pneumoniae (Spn) colonizes the nasopharynx asymptomatically but can also cause severe life-threatening disease. Importantly, stark differences in carbohydrate availability exist between the nasopharynx and invasive disease sites, such as the bloodstream, which most likely impact Spn's behavior. Herein, using chemically-defined media (CDM) supplemented with physiological levels of carbohydrates, we examined how anatomical-site specific carbohydrate availability impacted Spn physiology and virulence. Spn grown in CDM modeling the nasopharynx (CDM-N) had reduced metabolic activity, slower growth rate, demonstrated mixed acid fermentation with marked H₂O₂ production, and were in a carbon-catabolite repression (CCR)-derepressed state versus Spn grown in CDM modeling blood (CDM-B). Using RNA-seq, we determined the transcriptome for Spn WT and its isogenic CCR deficient mutant in CDM-N and CDM-B. Genes with altered expression as a result of changes in carbohydrate availability or catabolite control protein deficiency, respectively, were primarily involved in carbohydrate metabolism, but also encoded for established virulence determinants such polysaccharide capsule and surface adhesins. We confirmed that anatomical site-specific carbohydrate availability directly influenced established Spn virulence traits. Spn grown in CDM-B formed shorter chains, produced more capsule, were less adhesive, and were more resistant to macrophage killing in an opsonophagocytosis assay. Moreover, growth of Spn in CDM-N or CDM-B prior to the challenge of mice impacted relative fitness in a colonization and invasive disease model, respectively. Thus, anatomical site-specific carbohydrate availability alters Spn physiology and virulence, in turn promoting anatomical-site specific fitness.