PPSV23

PPSV23, the 23-valent pneumococcal polysaccharide vaccine, is a non-conjugate vaccine that protects against invasive disease caused by 23 serotypes of Streptococcus pneumoniae. It is marketed as Pneumovax 23 and manufactured by Merck. The vaccine is designed to stimulate antibody production against pneumococcal capsular polysaccharides.

Indications and populations commonly targeted include adults aged 65 years and older and younger people with certain risk factors. Risk factors may include chronic heart, lung, liver, or kidney disease; diabetes; alcoholism; smoking; asplenia or splenic dysfunction; HIV infection; malignancy or other conditions that compromise the immune system; and cochlear implants. Vaccination practices vary by country and over time, with PPSV23 often recommended in addition to other pneumococcal vaccines for specific groups.

Dosing and schedule generally involve a single dose for most adults 65 and older. Individuals who received PPSV23 before age 65 because of a high-risk condition may be advised to receive a second PPSV23 dose after reaching age 65, with at least a five-year interval between doses. In some guidelines, PPSV23 is used in combination with pneumococcal conjugate vaccines to optimize protection, depending on local recommendations.

Efficacy and limitations: PPSV23 covers serotypes responsible for a substantial portion of invasive pneumococcal disease in adults but is less effective against non-bacteremic pneumonia and may elicit a weaker immune response in some populations due to its T-independent mechanism. Conjugate vaccines generally offer better immunogenicity in children and in certain adult scenarios.

Administration and safety: PPSV23 is given by intramuscular injection, stored at 2–8°C, and generally well tolerated. Common side effects include injection-site pain, redness, swelling, and mild fever. Contraindications include a history of severe allergic reaction to a previous dose or to any component of the vaccine.