Background
Currently, the predominant onchocerciasis control strategy in Africa is annual mass drug
administration (MDA) with ivermectin. However, there is a consensus among the global
health community, supported by mathematical modelling, that onchocerciasis in Africa will
not be eliminated within proposed time frameworks in all endemic foci with only annual
MDA, and novel and alternative strategies are urgently needed. Furthermore, use of MDA
with ivermectin is already compromised in large areas of central Africa co-endemic with Loa
loa, and there are areas where suboptimal or atypical responses to ivermectin have been
documented. An onchocerciasis vaccine would be highly advantageous in these areas.
Methodology/Principal Findings
We used a previously developed onchocerciasis transmission model (EPIONCHO) to
investigate the impact of vaccination in areas where loiasis and onchocerciasis are coendemic
and ivermectin is contraindicated. We also explore the potential influence of a vaccination
programme on infection resurgence in areas where local elimination has been successfully
achieved. Based on the age range included in the Expanded Programme on
Immunization (EPI), the vaccine was assumed to target 1 to 5 year olds. Our modelling
results indicate that the deployment of an onchocerciasis vaccine would have a beneficial
impact in onchocerciasis–loiasis co-endemic areas, markedly reducing microfilarial load in
the young (under 20 yr) age groups.
Conclusions/Significance
An onchocerciasis prophylactic vaccine would reduce the onchocerciasis disease burden in
populations where ivermectin cannot be administered safely. Moreover, a vaccine could substantially decrease the chance of re-emergence of Onchocerca volvulus infection in
areas where it is deemed that MDA with ivermectin can be stopped. Therefore, a vaccine
would protect the substantial investments made by present and past onchocerciasis control
programmes, decreasing the chance of disease recrudescence and offering an important
additional tool to mitigate the potentially devastating impact of emerging ivermectin
resistance.