Evaluation of PCV15 Vaccination Among PPSV23-experienced, Immunocompromised Elderly Veterans

The investigators will evaluate the immune response of immunocompromised adults, who have previously received at least 1 dose of 23-valent pneumococcal polysaccharide vaccine, to the booster series of 15-valent pneumococcal conjugate vaccine followed by 23-valent pneumococcal polysaccharide vaccine 8 weeks later. Immune response will be assessed by opsonophagocytic assay reactivity and IgG Geometric mean concentration changes.

Recommendations for optimal vaccination strategies in immunocompromised patients has been limited. Strategies focused on utilizing a conjugate vaccine alone, as either initial vaccination or booster dosing, have not demonstrated significant increased antibody expression in immunocompromised patients. Strategies where immunocompromised patients were vaccinated with a conjugate vaccine followed by polysaccharide vaccine have demonstrated that 50% of individuals achieve functional antibodies. Since improved antibody response in naïve patients has been seen in combination vaccination, the investigators aim to test this strategy for boosting in previously vaccinated immunocompromised patients. The 15 valent Pneumococcal Conjugate Vaccine (PCV15) is available for use in adults and contains S. Pneumoniae serotypes 1, 3, 4, 6A, 7F, 9V, 14, 18C, 19A, 19F, 22F, 23F and 33F.

In this study the investigators postulate that booster dosing with PCV15 followed by PPSV23 8 weeks later in immunocompromised adults who are at least 5 years from receipt of PPSV23 will elicit a strong immune response represented by change in serotype specific opsonophagocytic assay(OPA) geometric mean titer (GMT) from baseline to 4 weeks post booster series completion. The investigators will specifically evaluate the change in immunoglobulin G (IgG) geometric mean concentrations (GMC) and pneumococcal opsonophagocytic activity at baseline to 6 months (Pn-OPA) for S. Pneumoniae serotypes 3, 22F, 33F, 9n, 8, 12F, and 20. These specific serotypes have been selected due to current disease burden trends, to address current gaps in data, and have been identified as the most relevant for Pneumococcal Conjugate Vaccine development underway.

In addition to the evaluating the combined response to PCV15 and PPSV23 booster dosing it is necessary to evaluate the impact of PCV15 alone to determine if single administration of PCV 15 in immunocompromised patients previously vaccinated with PPSV23 is a reasonable strategy.

Eligibility Criteria:
Inclusion Criteria:

* Subject meets the CDC definition of an immunocompromising condition

  o chronic renal failure, congenital or acquired asplenia, generalized malignancy, HIV infection, Hodgkin disease, iatrogenic immunosuppression, leukemia, lymphoma, multiple myeloma, nephrotic syndrome, sickle cell disease or other hemoglobinopathies, and solid organ transplant.
* Have received at least 1 dose of PPSV23

Exclusion Criteria:

* Less than 5 years since last receipt of PPSV23 validated to patient medical record and Immunize Nevada Website
* Previous administration of PCV20
* Previous administration of PCV13
* Less than 14 days since administration of any COVID19 vaccination
* Previous history of Invasive Pneumococcal Disease (IPD)
* Antibiotic treatment within the previous 90 days