Ebola vaccines in clinical trial: The promising candidates

Abstract

Ebola virus disease (EVD) has become a great threat to humans across the world in recent years. The 2014 Ebola epidemic in West Africa caused numerous deaths and attracted worldwide attentions. Since no specific drugs and treatments against EVD was available, vaccination was considered as the most promising and effective method of controlling this epidemic. So far, 7 vaccine candidates had been developed and evaluated through clinical trials. Among them, the recombinant vesicular stomatitis virus-based vaccine (rVSV-EBOV) is the most promising candidate, which demonstrated a significant protection against EVD in phase III clinical trial. However, several concerns were still associated with the Ebola vaccine candidates, including the safety profile in some particular populations, the immunization schedule for emergency vaccination, and the persistence of the protection. We retrospectively reviewed the current development of Ebola vaccines and discussed issues and challenges remaining to be investigated in the future.

Keywords: Ebola virus; clinical trial; efficacy; immunogenicity; safety; vaccine.

Figure 1.

Structure and functions of Ebola virus and Ebola virus genes. (A) Shown are the structure of Ebola virus which comprised of two main factors that nucleocapsid and envelope. In the middle of nucleocapsid and envelope is matrix which is comprised of VP40 and VP24. Glycoprotein spikes are located on the surface of envelope. (B) Shown are schematic representations of Ebola virus genome which is comprised of seven non-segmented genes. These seven genes encode the nucleoprotein, virion protein35, VP40, glycoprotein, VP30, VP24 and RNA-dependent RNA polymerase.

Figure 2.

Classification of Ebola vaccines. Ebola vaccines can be roughly divided into three classifies that non-replicative vector-based Ebola vaccines, replicative vector-based Ebola virus vaccines and other Ebola vaccines.

Figure 3.

Development history of Ebola virus vaccines. Shown are schematic representations of the sequence of development of Ebola virus vaccines and the start time of clinical trials. Each line represents the development of a kind of vaccine with its name ahead. The red triangle represents the start point of clinical trials of promising candidate. Almost every vaccine continues research up to date except inactivated vaccine which was stopped in 2002.