Pneumonia is an infection causing inflammation in the air sacs of one or both lungs, often leading to them filling with fluid or pus. This inflammation can be caused by various organisms, including bacteria, viruses, and fungi. While vaccines are available, protection is not absolute. A vaccinated person can still develop pneumonia because the condition is not caused by a single germ, and the available vaccines are highly specific in their targets. Understanding the scope of vaccine protection and other potential causes of lung infection is important.
The Specific Pathogens Targeted by Vaccination
The vaccines commonly referred to as the “pneumonia vaccine” are specifically designed to protect against disease caused by the bacterium Streptococcus pneumoniae. This bacterium, also known as pneumococcus, is the most common cause of bacterial pneumonia acquired outside of a healthcare setting. The pneumococcal vaccines work by introducing inactive components of the bacteria to the immune system, training the body to recognize and fight off a future infection.
There are two main types of pneumococcal vaccines: the pneumococcal conjugate vaccines (PCV) and the pneumococcal polysaccharide vaccine (PPSV). These vaccines differ in the number of bacterial strains, or serotypes, they cover.
The number on the vaccine name, such as PCV20 or PPSV23, indicates the quantity of serotypes the shot protects against. While the vaccines cover the most prevalent and serious strains of the pneumococcus bacteria, there are over 90 different serotypes in existence. Protection is serotype-specific, meaning the vaccine only provides immunity against the exact strains it contains. This explains one way a vaccinated person can still contract bacterial pneumonia: from a pneumococcal serotype not included in the vaccine formulation.
Understanding Non-Vaccine Related Pneumonia
Pneumococcal vaccines do not protect against the many other germs that can cause pneumonia, which is the primary reason why a vaccinated person can still become ill. The infection can be caused by a wide range of pathogens, including other bacteria, viruses, and fungi.
Viral infections are a frequent cause of pneumonia and a common precursor to bacterial infection. Viruses like influenza, Respiratory Syncytial Virus (RSV), and COVID-19 can damage the lining of the respiratory tract, making the lungs vulnerable to secondary bacterial invaders. The pneumococcal vaccine provides no direct protection against these viral causes.
Pneumonia can also be caused by other bacteria besides Streptococcus pneumoniae. Common examples include Haemophilus influenzae, Mycoplasma pneumoniae, and Legionella pneumophila. Although vaccines exist for some of these, such as Haemophilus influenzae type b (Hib), the standard pneumococcal vaccine does not cover these pathogens.
In some cases, pneumonia is not caused by an infection at all. Aspiration pneumonia occurs when foreign materials like food, liquid, or stomach contents are inhaled into the lungs. Additionally, inhaling toxic chemicals or environmental irritants can lead to inflammation that mimics pneumonia. Since these types of lung inflammation are not caused by the targeted bacteria, vaccination offers no defense against them.
Layered Prevention Strategies
To reduce the overall risk of pneumonia, people should adopt a strategy that goes beyond the pneumococcal vaccine. This layered approach focuses on preventing the viral infections that often lead to pneumonia and strengthening the body’s defenses. Getting a yearly influenza vaccine is a straightforward way to reduce the risk of flu-related pneumonia.
Other vaccinations, such as those for COVID-19 and RSV, also contribute to overall respiratory health protection. These shots help prevent viral illnesses that can either directly cause pneumonia or weaken the immune system, making a person susceptible to a secondary bacterial infection. Staying up to date on all recommended immunizations provides a broader shield against various respiratory threats.
Lifestyle factors and hygiene practices are also important for prevention. Regular handwashing removes germs that can cause respiratory infections. Avoiding smoking is important, as tobacco smoke damages the lungs’ natural defense mechanisms. Managing underlying chronic health conditions like asthma, diabetes, and heart disease helps keep the immune system stronger and reduces susceptibility to infections.