http://goo.gl/IKGfXx
Mr. R, my 67-year-old patient who already received Pneumovax23, was not enthusiastic about the idea. “But I already got one! Why do I need another? What is the difference from the one I already got?”
All good questions. Let’s look closely at the guidelines to see if we can answer these questions.
What is the difference between Pneumovax23 and Prevnar13?
Pneumovax23 stands for pneumococcal polysaccharide vaccine (23-valent). First used in 1945, it was an important landmark in medical history. Pneumovax23 was the first pneumonia vaccine, and the first to be made from capsular polysaccharide, which can help induce immunity in host body. It is called 23-valent because it aims to protect against 23 types of pneumococcal capsules, which translates to 50-80% efficacy2.
Prevnar13 stands for pneumococcal conjugate vaccine (13-valent). It is made from bacterial cell membrane sugars conjugated with a diphtheria toxin protein called CRM197 to induce a stronger immune response. It is traditionally given to children and adults over 19 years old with certain medical conditions (lack of spleen, compromised immune system, etc.) It is called 13-valent because it aims to protect against 13 types of pneumococcal capsules, 12 of which were exactly the same as the ones covered by Pneumovax23. The only serotype covered by Prevnar13, but not by Pneumovax23, is serotype 6A.
Why would we want to add Prevnar13 to Pneumovax23, which adults 65 and older were already getting?
It turns out that a percentage of severe illness in older adults is caused by the types of pneumococcal bacteria that Prevnar13 can protect against. For example, 20-25% of a disease entity called invasive pneumococcal disease (such as meningitis, bacteremia) is caused by bacterial serotypes that Prevnar13 covers1. It should be noted that even though Pneumovax23 covers these similar serotypes, it is stipulated that Prevnar13 will be more effective, because its conjugated protein should induce a stronger immune response than Pneumovax23.