The Impact

The Impact

A vaccine will be of greatest benefit to children and young adults.

Modelling analyses (Figure 8) have shown that an onchocerciasis vaccine will have a substantial impact in a range of endemicity scenarios and will markedly reduce microfilarial load in those under 20 years of age (https://doi.org/10.1371/journal.pntd.0003938). This has important implications as studies have highlighted the increased risk of developing onchocerciasis-related morbidity and mortality in individuals who acquire heavy infections in early life. A vaccine would have a beneficial impact by reducing onchocerciasis-related disease burden in these populations. Furthermore, a vaccine could markedly decrease the chance of recrudescence of onchocerciasis in areas where MDA treatment has stopped.

A vaccine is probably the only tool that could prevent infection in very young children for their personal benefit. Young children have been completely neglected in onchocerciasis control efforts to date because they rarely show any symptoms of disease. Nevertheless, modelling data indicate that they are affected by excess mortality attributable to onchocerciasis (https://doi.org/10.1371/journal.pntd.0001578), and it should not be assumed that they will always receive ivermectin later in life to prevent disease symptoms (for instance, due to residence in loiasis-endemic areas or migration from their community of origin).

Added value

A vaccine would protect the substantial investments made by present and past onchocerciasis control programmes (the Onchocerciasis Control Programme, OCP; and the African Programme for Onchocerciasis Control, APOC; over US$1 billion), by reducing the chance of disease recrudescence and the inevitable spread of ivermectin resistance.

The vaccine may also find application in a therapeutic role in individuals already infected with O volvulus.

Beyond onchocerciasis, it may be possible to apply the vaccine (with or without reformulation) to control of lymphatic filariasis.  A veterinary application may be found in control and prevention of canine heartworm (Dirofilaria immitis).

The impact of childhood vaccination