American Board of Internal Medicine (ABIM) Certification Practice Exam 2026 - Free ABIM Practice Questions and Study Guide

The recommended order for pneumococcal vaccinations in immunocompromised individuals is to administer the 13-valent pneumococcal conjugate vaccine (PCV13) followed by the 23-valent pneumococcal polysaccharide vaccine (PPSV23). This sequence is crucial because PCV13 helps to prime the immune response, which enhances the effectiveness of the subsequent PPSV23 vaccination.

PCV13 contains conjugated polysaccharide antigens, which leads to a more robust T-cell dependent immune response, especially important in immunocompromised patients who may have a diminished response to polysaccharide vaccines alone. Following PCV13, PPSV23 is administered at least 8 weeks later to provide broader coverage against the bacteria responsible for causing serious infections, as PPSV23 contains polysaccharide antigens that cover more serotypes, thereby enhancing protection.

This specific order and timing are essential in optimizing immune response and ensuring that immunocompromised individuals receive the best protection against pneumococcal disease. The other choices either reverse the order or suggest using one type of vaccine only, which does not adhere to the recommended guidelines set forth by health authorities such as the Centers for Disease Control and Prevention (CDC).