Three New Ebola Vaccines Demonstrate Persistent Immune Response

ebola antibody
ebola antibody
The immunogenicity generated by 3 experimental Ebola vaccines appears to be long-lasting, as it has persisted for at least 2.5 years.

The immunogenicity generated by 3 experimental Ebola vaccines appears to be long-lasting, as it has persisted for at least 2.5 years, according to data presented at the Annual Meeting of the American Society of Tropical Medicine and Hygiene held October 28-November 1, 2018 in New Orleans, Louisiana.

Of the vaccines developed following the 2014-2016 Ebola outbreak in West Africa, early stage clinical trials showed that 3 candidates that encoded the Zaire Ebola glycoprotein demonstrated acceptable reactogenicity and promising immunogenicity. One vaccine candidate was a single-dose approach based on a replicating vesicular-stomatitis virus (rVSV ZEBOV) and the two others were heterologous prime-boost combinations using replication-deficient adenoviruses (ChAd3 and AdHu26) to prime and the multivalent MVA BN-Filo to boost. Although the rVSV ZEBOV vaccine showed 100% short-term efficacy in a phase 3 ring vaccination trial after exposure to Ebola virus disease cases, durability has not yet been evaluated.

Clinical trials of both prime-boost regimes have been followed up to determine the durability of both humoral and cellular immunity, and the results show that 91% of 43 recipients of the AdHu26/MVA vector vaccine had positive glycoprotein-specific IgG titers at 2.5 years post-immunization, as did 54% of 13 recipients of Chad3/MVA vectored vaccines. In addition, rVSV ZEBOV was administered in 2015 to 26 contacts of a healthcare worker infected with Ebola virus in Sierra Leone, who recovered and then subsequently relapsed. Samples from this cohort will allow for comparison of immunogenicity using a standardized enzyme-linked immunosorbent assay (ELISA) and validated enzyme-linked immunospot (ELISPOT) assay to determine humoral and cellular immunity against the Zaire Ebola virus glycoprotein. In addition, samples that were obtained 2.5 years post-vaccination will also be compared to determine whether there are differences in quality, quantity, and persistence of immunity.

 “These data are important for long-term strategic planning for prophylactic protection of front-line healthcare workers in regions at risk of future outbreaks,” concluded the investigators.

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Ewer K, Smith C, Sarlar E, at al. Durability of immune responses induced by three leading candidate Ebola vaccine regimes; rVSV ZEBOV, ChAd3 EBO Z-MVA BN-Fila an dAdHu26.ZEBOV-MVA BN Filo. Presented at: ASTMH Annual Meeting; October 28-November 1, 2018; New Orleans, Louisiana. Abstract 685.