Why is Menactra preferred over Menomune?
Menomune (MPSV) is a pure polysaccharide vaccine. Because the immune response to a pure polysaccharide vaccine is T-cell independent, the antibody induced has less functional activity than that induced by other types of vaccines. This is because the predominant antibody produced in response to most polysaccharide vaccines is IgM, with little IgG antibody being produced. Also, repeat doses of polysaccharide vaccines do not stimulate a booster response. Conjugation (chemical combination of the polysaccharide with a protein molecule) changes the immune response from T-cell independent to T-cell dependent. This increases immunogenicity and the antibody booster response. Because the polysaccharides in Menactra (MCV) are conjugated to diphtheria toxoid, it is believed that this vaccine will have a longer duration of protection than MPSV. In addition, MCV is expected to reduce asymptomatic carriage of Neisseria meningitidis and produce “herd” immunity, as occurs with Streptococcus pneumoniae
