[Katchit (OP)]

Hello everyone ; im new here ; looks like a busy forum! In terms of immunity ; why is it that MCV-4 lasts longer than MPSV? Thank you.

[CliffordK]

Here is a note in Wikipedia about Meningococcal Vaccines.

There are currently three vaccines available in the US to prevent meningococcal disease, all quadrivalent in nature, targeting serogroups A, C, W-135 and Y:

• two conjugate vaccines (MCV-4), Menactra and Menveo, and
• one polysaccharide vaccine (MPSV-4), Menomune, produced by Sanofi Pasteur.

Limitations
The duration of immunity mediated by Menomune (MPSV4) is three years or less in children aged under 5 because it does not generate memory T cells.  Attempting to overcome this problem by repeated immunization results in a diminished not increased antibody response, so boosters are not recommended with this vaccine.  As with all polysaccharide vaccines, Menomune does not produce mucosal immunity, so people can still become colonised with virulent strains of meningococcus, and no herd immunity can develop.  For this reason, Menomune is suitable for travelers requiring short-term protection, but not for national public health prevention programs.

Menveo and Menactra [MCV-4] contain the same antigens as Menomune, but the antigens are conjugated to a diphtheria-toxoid polysaccharide–protein complex, resulting in anticipated enhanced duration of protection, increased immunity with booster vaccinations, and effective herd immunity.
Endurance
A study published in March 2006 comparing the two kinds of vaccines found that 76% of subjects still had passive protection three years after receiving MCV-4 (63% protective compared with controls), but only 49% has passive protection after receiving MSPV-4 (31% protective compared with controls).  As of 2010, there remains limited evidence that any of the current conjugate vaccines offer continued protection beyond three years; studies are ongoing to determine the actual duration of immunity, and the subsequent requirement of booster vaccinations. The CDC offers recommendations regarding who they feel should get booster vaccinations.

So, by combining the vaccine with a Diphtheria protein, it seems to have more respiratory type responses, as well as better Mucosal immunity and Memory T cell immunity.

One should note that most children are also vaccinated with DPT (Diphtheria, Pertussis, Tetanus).