[2] This is usually accomplished with an attenuated or dead version of a pathogenic bacterium or virus in the vaccine, so that the immune system can recognize the antigen later in life.
In this case, a conjugate vaccine is used in order to invoke an immune system response against the weak antigen.
[3] The idea of a conjugate vaccine first appeared in experiments involving rabbits in 1927, when the immune response to the Streptococcus pneumoniae type 3 polysaccharide antigen was increased by combining the polysaccharide antigen with a protein carrier.
In the case of a conjugate vaccine, the carrier peptide linked to the polysaccharide target antigen is able to be presented on the MHC molecule and the T cell can be activated.
This improves the vaccine as T cells stimulate a more vigorous immune response and also promote a more rapid and long-lasting immunologic memory.
[6] Both Streptococcus pneumoniae and Neisseria meningitidis are similar to Hib in that infection can lead to meningitis.