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Understanding How the Pneumococcal Conjugate Vaccine Prevents Pneumococcal Infections
Now that we know who is eligible for the pneumococcal conjugate vaccine and when to get it, it’s time to talk about how it works and its benefits.
For starters, pneumococcal infections are diseases caused by the bacteria Streptococcus pneumoniae. While pneumonia often first comes to mind, this gram-positive bacteria can also cause inner ear infections (otitis media), sepsis, and meningitis⁵. Like other bacterial infections, there are antibiotics available to treat these infections if they happen. Unfortunately, S. pneumoniae is becoming more resistant to these drugs, making vaccination and prevention the best option.
The pneumococcal conjugate vaccine contains special sugar molecules called polysaccharides from different serotypes of S. pneumoniae. Pneumococcal conjugate vaccine protects against 13 of the most common serotypes. This is a purified material from the capsule or coating of the bacteria, therefore it does not contain the actual bacteria or infectious material. The polysaccharide molecules are paired with a carrier protein, resulting in a conjugated vaccine.
Inside the body, the vaccine works by activating white blood cells known as T cells. The protein-polysaccharide compound activates T cells which then signals another type of immune cell known as B cells. B cells are responsible for producing antibodies (IgM and IgG) and memory B cells which are essential for long-term immunity4, 6. Antibodies help the immune system quickly identify and efficiently attack infectious pathogens, such as S. pneumoniae, when a person is exposed to it.
Effectiveness of the Vaccine
After getting the vaccine, it takes several weeks before the body develops enough antibodies against pneumococcal infections. Therefore, it is important to prevent exposure to and close contact with infected individuals during this time. In terms of efficacy, the pneumococcal conjugate vaccine is up to 100% effective at preventing invasive pneumococcal infections in infants who are given 4 doses starting at 4 months of age.
Based on results of a Community-Acquired Pneumonia Immunization Trial in Adults (CAPiTA) aged 65 years and older, PCV is 75% effective against invasive pneumococcal diseases. Additionally, the vaccine has 45% efficacy against non-invasive pneumococcal pneumonia².