The Impact of Ebola Vaccination on Mortality Rates: Insights from Recent Studies

Recent studies have shed light on the effectiveness of Ebola vaccination, showing that even post-exposure, the vaccine can significantly reduce the risk of death among infected individuals. This research, focused on the 2018-2020 Ebola outbreak in the Democratic Republic of the Congo, bolsters the case for vaccination as a critical tool in controlling Ebola outbreaks.

A Closer Look at the Studies

Published in the Lancet Infectious Diseases, one study revealed that the risk of dying from Ebola was halved among people vaccinated with a single dose of Merck's Ervebo. Remarkably, the protective effect of the vaccine seemed to increase over time; the longer it had been since a patient had been vaccinated, the better their chances of surviving. Among those vaccinated three to nine days before developing symptoms, the fatality rate was 20%, dropping even further to 18% for those vaccinated 10 or more days before symptom onset.

Another study conducted by Epicentre, the medical research and epidemiology centre of Médecins Sans Frontières (MSF), echoed these findings. Analysis of data from the 10th Ebola epidemic in the DRC showed a significant reduction in mortality rates, from 56% among unvaccinated patients to 25% for those who had received the rVSVΔG-ZEBOV-GP vaccine, currently recommended for use during Ebola epidemics.

The Vaccine’s Impact on Viremia and Mortality

These studies also revealed a link between the Ebola vaccine and lower viremia, or the presence of the virus in the blood. Patients who had been vaccinated showed significantly higher cycle threshold values for nucleoprotein, indicating lower viremia. This reduction in viremia could be key to the vaccine’s role in lowering case fatality risk, as a smaller viral load may lead to a less severe disease course.

Moreover, the research also showed that combining vaccination with treatment for patients who have been in direct contact with a person with confirmed Ebola could further reduce the risk of illness and death. This suggests an additive effect when vaccination is paired with other therapeutic interventions.

The Importance of Vaccination in Outbreak Settings

The findings of these studies underscore the importance of early vaccination efforts in outbreak settings, as the protective effect of the vaccine against death grew with increased time from vaccination to symptom onset. The data also supports the use of the vaccine as post-exposure prophylaxis, meaning it can be administered to people who have been exposed to the virus but are not yet showing symptoms.

These insights provide valuable guidance for future Ebola outbreak responses and suggest that, even after exposure, Ebola vaccination can be a lifesaving intervention. While more research is needed to further understand and optimize the use of Ebola vaccines, these findings mark a significant step forward in the global fight against this devastating disease.