This boy has meningitis caused by Strep pneumoniae, the most common cause of infectious meningitis in general. The vaccine for Strep pneumo is a polysaccharide protein conjugate vaccine. The other major bacteria with a vaccine like this is H. influenzae.
so I thought in kids/elderly you give the diptheria-toxoid conjugate vaccine and adults you give the polysacc conjugate. why does this kid get the polysacc conjugate?
PCV13 for strep pneumo is polysaccharide conjugated to diptheria toxin-like protein (FA20-105). This is needed for a T-cell dependent response which allows for class switching and production of IgG Ab. This is a much more robust immune response. This provides memory and is why the vaccine is given at an early date.
On the contrary, antigens lacking a protein (such as the capsular polysaccharide) such as PPSV23 vaccine are not presented to T-cells, and therefore have a much weaker response + do not class switch.
Pneumococcal conjugate vaccines are strongly immunogenic in infancy due to both B and T cell recruitment. They provide higher, longer-lasting antibody titers relative to pneumococcal polysaccharide vaccines. The pneumococcal polysaccharide vaccine is poorly immunogenic in infants due to their relatively immature humoral antibody response.
Source: UWORLD
submitted by โsuckitnbme(239)
There are two types of pneumococcal vaccines for Strep pneumoniae.
The pneumococcal conjugate vaccine (PCV13) is given to children under 5. It is also given to adults age >=65 who are immunocompromised (PPSV23 is also given afterwards).
The polysaccharide vaccine PPSV23 is given to adults, the indications for which I won't go into.
Since this patient is 2-years old he should have received the conjugate vaccine per CDC guidelines.