Malaria is still a leading cause of morbidity and mortality in human popula
tions. Problems, including drug-resistant parasites and insecticide resista
nt mosquitoes, ensure the continued hold of malaria in the tropics and sub-
tropics. Each year around 100 million cases of malaria result in at least 5
0,000 deaths outside of sub-Saharan Africa; within sub-Saharan Africa itsel
f, malaria causes around one million child deaths per year. New approaches
for malaria control are badly needed and much effort has gone to develop ma
laria vaccines. In addition to giving personal protection, most such vaccin
es would also tend to reduce the transmission of malaria. One class of vacc
ine is being developed specifically for this purpose - the malaria transmis
sion-blocking vaccines (TBV). TBVs are based upon antigens expressed on the
surface of the sexual and mosquito mid-gut stages of malaria parasites. Th
ese antigens are the targets of antibodies induced by vaccination of the ho
st and ingested with the parasites in a mosquito blood meal. The antibodies
act by inhibiting the parasite's development within the mosquito itself an
d they thereby prevent the onward transmission of the parasites. TBVs could
contribute to the total interruption of malaria transmission in many locat
ions with relatively low transmission rates, mostly outside sub-Saharan Afr
ica. Under almost all transmission rates, however, TBVs would help reduce m
alaria incidence and malaria-related morbidity and mortality. Promising rec
ombinant TBV candidate antigens for the two main human malaria parasite spe
cies, Plasmodium falciparum and Plasmodium vivax, have been produced and te
sted in the laboratory, one has undergone early clinical trials.