The Vaccine

The Vaccine

Vaccine candidates

The TOVA Partnership has identified three candidate vaccine antigens that have proven to be efficacious in three different filarial animal model systems and in five independent laboratories (Table 3).

Protecting children, reducing morbidity and transmission

Children: the neglected hosts

Children below 5 years are excluded from ivermectin treatment and this leaves a significant proportion of the population exposed to infection. For example, in Cameroon [2015], 16% of the population are under 5 years. (United Nations, http://esa.un.org/unpd/wpp/index.htm). Similar age profiles are found throughout filarial endemic regions of Africa and in populations that are expected to double over the next 25 years (https://www.populationpyramid.net/sub-saharan-africa/2050.htm). Pre-school children comprise a large reservoir of microfilariae that can contribute to transmission. Furthermore, for the individual, the consequences of not receiving treatment would be the prospect of developing progressive filarial disease and more general long-term health problems as well as associated socio-economic disadvantage. Vaccination would protect the individual and make a major contribution to public health.

Our goal is production and testing of a river blindness vaccine through Phase I trials by 2025.

It is envisaged that the onchocerciasis vaccine will be used initially to protect vulnerable children (<5 years of age) living in loiasis co-endemic areas. The vaccine will reduce adult worm burden and fecundity with consequential reduction in pathology associated with microfilariae (Figure 3). In addition, a vaccine will find use in ongoing ivermectin MDA areas and contribute to reduction in transmission rates; and, will protect areas where local elimination may have been achieved.

 

Table 3, Onchocerciasis (river blindness) vaccine candidates
Percentages represent killing in vitro by human antigen-specific antibodies with neutrophils, or reduction in parasite burden in vivo. ES, excreted-secreted antigens. rProtein, recombinant protein. Ov, Onchocerca volvulus. Bm, Brugia malayi. Ls, Litomoso