Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design.
<h4>Background</h4>Lassa fever (LF) is an acute viral hemorrhagic disease endemic to West Africa that has been declared a priority disease by the World Health Organization due to its severity and the lack of a vaccine or effective treatment options. Several candidate vaccines are current...
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| Format: | Article |
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Public Library of Science (PLoS)
2025-07-01
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| Series: | PLoS Neglected Tropical Diseases |
| Online Access: | https://doi.org/10.1371/journal.pntd.0012751 |
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| author | Sean M Moore Erica Rapheal Sandra Mendoza Guerrero Natalie E Dean Steven T Stoddard |
| author_facet | Sean M Moore Erica Rapheal Sandra Mendoza Guerrero Natalie E Dean Steven T Stoddard |
| author_sort | Sean M Moore |
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| description | <h4>Background</h4>Lassa fever (LF) is an acute viral hemorrhagic disease endemic to West Africa that has been declared a priority disease by the World Health Organization due to its severity and the lack of a vaccine or effective treatment options. Several candidate vaccines are currently in development and are expected to be ready for phase III field efficacy trials soon. However, most LF cases and deaths are believed to go unreported, and as a result we lack a clear understanding of several aspects of LF epidemiology and immunology that are critical to the design of vaccine efficacy trials.<h4>Methods</h4>To help guide vaccine trial design and trial site selection we estimated the force of infection (FOI) from rodent hosts to humans in all 1st and 2nd administrative units in West Africa from published seroprevalence studies. We next estimated LF reporting probabilities using these FOI estimates and LF case and death reports and then projected FOI in all admin1 and admin2 areas without seroprevalence data. We then extrapolated age-specific LF incidence rates from FOI estimates under different assumptions regarding the level of protection against reinfection among seropositive and seronegative individuals with a history of prior infection.<h4>Results</h4>Projected FOI estimates and modeled annual LF incidence rates indicate that Sierra Leone, southern Guinea, and a few areas within Nigeria would likely experience the highest LF case incidence rates for a vaccine trial. Estimated LF incidence rates were highly sensitive to assumptions about Lassa immunology, particularly the frequency of seroreversion among previously infected individuals and the extent to which seroreverted individuals retain protection against reinfection and more severe disease outcomes.<h4>Conclusions</h4>Our spatial LF incidence rate estimates, along with the interannual and seasonal variability in these estimates and estimates of baseline seroprevalence, could be used for vaccine trial site selection, choosing the target population (e.g., age and serostatus), and maximizing a trial's statistical power. |
| format | Article |
| id | doaj-art-a24947d998cc4a96b36db94e7bc212c6 |
| institution | Kabale University |
| issn | 1935-2727 1935-2735 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | Public Library of Science (PLoS) |
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| series | PLoS Neglected Tropical Diseases |
| spelling | doaj-art-a24947d998cc4a96b36db94e7bc212c62025-08-20T03:40:21ZengPublic Library of Science (PLoS)PLoS Neglected Tropical Diseases1935-27271935-27352025-07-01197e001275110.1371/journal.pntd.0012751Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design.Sean M MooreErica RaphealSandra Mendoza GuerreroNatalie E DeanSteven T Stoddard<h4>Background</h4>Lassa fever (LF) is an acute viral hemorrhagic disease endemic to West Africa that has been declared a priority disease by the World Health Organization due to its severity and the lack of a vaccine or effective treatment options. Several candidate vaccines are currently in development and are expected to be ready for phase III field efficacy trials soon. However, most LF cases and deaths are believed to go unreported, and as a result we lack a clear understanding of several aspects of LF epidemiology and immunology that are critical to the design of vaccine efficacy trials.<h4>Methods</h4>To help guide vaccine trial design and trial site selection we estimated the force of infection (FOI) from rodent hosts to humans in all 1st and 2nd administrative units in West Africa from published seroprevalence studies. We next estimated LF reporting probabilities using these FOI estimates and LF case and death reports and then projected FOI in all admin1 and admin2 areas without seroprevalence data. We then extrapolated age-specific LF incidence rates from FOI estimates under different assumptions regarding the level of protection against reinfection among seropositive and seronegative individuals with a history of prior infection.<h4>Results</h4>Projected FOI estimates and modeled annual LF incidence rates indicate that Sierra Leone, southern Guinea, and a few areas within Nigeria would likely experience the highest LF case incidence rates for a vaccine trial. Estimated LF incidence rates were highly sensitive to assumptions about Lassa immunology, particularly the frequency of seroreversion among previously infected individuals and the extent to which seroreverted individuals retain protection against reinfection and more severe disease outcomes.<h4>Conclusions</h4>Our spatial LF incidence rate estimates, along with the interannual and seasonal variability in these estimates and estimates of baseline seroprevalence, could be used for vaccine trial site selection, choosing the target population (e.g., age and serostatus), and maximizing a trial's statistical power.https://doi.org/10.1371/journal.pntd.0012751 |
| spellingShingle | Sean M Moore Erica Rapheal Sandra Mendoza Guerrero Natalie E Dean Steven T Stoddard Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design. PLoS Neglected Tropical Diseases |
| title | Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design. |
| title_full | Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design. |
| title_fullStr | Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design. |
| title_full_unstemmed | Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design. |
| title_short | Estimation of Lassa fever incidence rates in West Africa: Development of a modeling framework to inform vaccine trial design. |
| title_sort | estimation of lassa fever incidence rates in west africa development of a modeling framework to inform vaccine trial design |
| url | https://doi.org/10.1371/journal.pntd.0012751 |
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