Maternal inhibition of malaria vaccination in mice can be overcome by giving a second dose of vaccine.

A single dose of a formalin-fixed malaria vaccine which normally protects mice against challenge with the live parasite, is ineffective in mice born to immune mothers. This inhibition of protection, which is due to maternally-derived IgG, can be overcome if a second dose of vaccine is given 10 or more days after the first. We show that this is related to the production of specific IgM antibody in response to the first dose of vaccine, which competitively blocks the inhibitory effect of the IgG. The implications of this finding in relation to immune regulation and immunization regimes are discussed.