Pneumonia is a serious infection causing inflammation of the air sacs in the lungs, often caused by the bacterium Streptococcus pneumoniae (pneumococcus). Vaccination plays an important role in protecting adults from pneumococcal disease, which includes pneumonia, and other serious infections like meningitis and bloodstream infections. These vaccines help the body develop defenses against the bacteria.
Pneumonia Vaccine Types and Their Protection Lifespan
Two main categories of pneumococcal vaccines are available for adults: pneumococcal conjugate vaccines (PCV) and pneumococcal polysaccharide vaccines (PPSV23). These vaccines differ in how they stimulate the immune system and in their duration of protection. PCV types, such as PCV13, PCV15, PCV20, and the newer PCV21, induce a T-cell dependent immune response. This leads to the formation of memory B cells, which provides a more robust and longer-lasting immunity.
Pneumococcal conjugate vaccines offer durable, long-term protection, with some sources suggesting potentially lifelong immunity for certain PCV types in older adults. PCV13 protects against 13 serotypes, PCV15 against 15, PCV20 against 20, and PCV21 against 21 specific types of Streptococcus pneumoniae. When PCV20 or PCV21 is administered, it provides comprehensive protection, meaning additional doses of PPSV23 are generally not indicated.
In contrast, PPSV23 contains purified capsular polysaccharides from 23 different serotypes. This vaccine primarily elicits a B-cell dependent, T-cell independent immune response. While effective, this mechanism does not generate the same level of immune memory as conjugate vaccines.
Protection from PPSV23 wanes over time. Antibody levels often return to near pre-vaccination levels within 4 to 7 years post-vaccination, meaning its efficacy diminishes after approximately five years.
Factors Influencing Vaccine Effectiveness and Revaccination
Several factors influence vaccine effectiveness and the need for revaccination in adults. Age is a significant consideration, as older adults, particularly those aged 65 and above, face an increased risk of severe pneumococcal disease and may experience a decline in immune response. Public health guidelines emphasize vaccination for this demographic.
Underlying health conditions also play a substantial role in vaccine effectiveness and duration. Individuals with immunocompromising conditions, such as HIV infection, chronic kidney failure, or certain cancers, have an elevated risk of pneumococcal disease. Chronic diseases like heart disease, lung disease, diabetes, and chronic liver disease also increase vulnerability. Conditions like cerebrospinal fluid (CSF) leaks or a cochlear implant also indicate higher risk. These factors can impact the body’s ability to mount a strong or sustained immune response.
Revaccination recommendations are tailored to an individual’s age, health conditions, and previous vaccination history. For adults who receive PCV15, a follow-up dose of PPSV23 is advised at least one year later. If PCV20 or PCV21 is administered, generally no further pneumococcal vaccine doses are needed. For those who previously received PPSV23, revaccination with another dose may be considered at least five years after the initial dose, especially for high-risk individuals or if the first dose was given before age 65. The Centers for Disease Control and Prevention (CDC) updated recommendations in October 2024 to include adults aged 50 and older.