Onchocerca volvulus infective L3
Microfilariae in uterus of Onchocerca volvulus
Onchocerca nodules on head of pre-school child, Cameroon

2020 vision of a vaccine against river blindness

The Onchocerciasis Vaccine for Africa (TOVA) Initiative has been launched as a response to the London Declaration on Neglected Tropical Diseases; and, the scientific and technical demands for new tools to complement ivermectin MDA to ensure elimination of onchocerciasis from Africa.

TOVA has its origins in the river blindness (onchocerciasis) vaccine program of the Edna McConnell Clark Foundation (1985-1999) and subsequently supported by European Union through its Directorate-General for Research and the US NIH National Institute of Allergy and Infectious Diseases. These investments have combined development of animal models and human studies of protective immunity with molecular and post genomic analyses of filarial parasites.

Three vaccine candidates have been identified through their proven efficacy in three different filarial animal models in three independent laboratories. TOVA aims to take at least one of these experimental vaccines through phase 1 safety trials by 2022.

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 where ivermectin is contra-indicated because of the risk of severe adverse reactions. The vaccine will reduce adult worm burden and fecundity with consequential reduction in pathology associated with microfilariae. In addition, a vaccine will find use in ongoing ivermectin MDA areas and contribute to reduction in transmission rates.

Mathematical modelling by Imperial College, London has shown that a river blindness vaccine will have substantial impact in a range of endemicity scenarios and will markedly reduce microfilarial load in those under 20 years of age. 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), by reducing the chance of disease recrudescence and the inevitable spread of ivermectin resistance.

TOVA brings a consortium of African and European scientists, who have worked together on river blindness since the mid 1980’s, together with US laboratories that have a similar history of investigation of filarial infections. The expanded partnership of TOVA will use the best practice of product development from the Texas Children’s Hospital Center for Vaccine Development to bring the vaccine candidates to human safety trials by 2022. The mathematical modelling skills of Imperial College, London will help design of control programmes to maximise access and delivery of the vaccine to target communities.

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