Comparative Evaluation of Five Lassa Virus IgG Immunoassays for Seroprevalence Studies and Vaccine Trial Support in West Africa

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Introduction Serological testing is pivotal in diagnosing Lassa fever and conducting sero-epidemiological studies essential for planning vaccine efficacy trials in endemic regions. However, comparative data on the performance of available Lassa virus (LASV) serologic assays remain limited. To support clinical trials in West Africa, we conducted a comparative evaluation of five LASV-specific IgG immunoassays to determine their diagnostic utility. Methods This diagnostic evaluation study was performed at the Irrua Specialist Teaching Hospital, Nigeria, and Kenema Government Hospital, Sierra Leone. A total of 148 archived LASV-RT-PCR-positive sera from Nigeria and 158 LASV-antigen-positive sera from Sierra Leone were tested. LASV-naïve sera from Gabon served as negative controls. The U.S. CDC LASV IgG assay was used as the reference test. Positive percentage agreement (PPA) and negative percentage agreement (NPA) were calculated against either the reference assay or the expected clinical classification based on historical data and sample origin. Country-specific performance metrics were computed for LASV-exposed and LASV-naïve samples. Results Among LASV-positive cases by clinical category, 123/158 (Sierra Leone) and 104/148 (Nigeria) were IgG-positive using the reference assay. Four of the five evaluated immunoassays demonstrated PPA ≥90% compared to the reference. Two assays exhibited NPA ≥95% in both countries. Country-level findings aligned with combined analyses, with slightly improved NPA among LASV-naïve versus LASV-exposed but seronegative individuals. Conclusion Among the five evaluated IgG assays, the BLACKBOX Lassa NP-IgG ELISA and Lassa IgG DABA ELISA demonstrated high sensitivity and specificity. These assays are suitable for LASV seroprevalence studies and may reliably support future Lassa fever vaccine trials in West Africa.

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