A new study published in the journal Lancet Infectious Diseases has reported that Merck’s Ebola vaccine, Ervebo, provided substantial protection to individuals vaccinated during the 2018-2020 outbreak in the Democratic Republic of the Congo. The study found that the vaccine had an effectiveness of 84% in those who had been vaccinated at least 10 days before being exposed to the virus. Additionally, the study revealed that individuals who were vaccinated but still developed the disease were more likely to survive the infection.
The effectiveness estimate of 84% from this real-world study is lower than the 100% efficacy estimate from the Ebola Ça Suffit! trial in Guinea and the 97.5% preliminary effectiveness estimate from the DRC’s National Institute for Biomedical Research and the World Health Organization. However, it was expected that the real-world effectiveness would be lower than clinical trial efficacy estimates, as no vaccine provides complete protection to everyone who receives it.
The study was conducted by researchers from the DRC Ministry of Health, the INRB, the University of Kinshasa, and Doctors Without Borders (MSF). The data for the study was collected from the database set up during the 2018-2020 outbreak in North Kivu and Ituri provinces. This outbreak was the second largest on record, resulting in nearly 3,500 confirmed infections and almost 2,300 deaths.
The Merck Ebola vaccine, Ervebo, is one of only two licensed Ebola vaccines and is recommended for use as an outbreak response tool due to its single-dose administration. The study authors calculated the vaccine effectiveness estimate based on the data collected during the outbreak, showing that in a group of vaccinated individuals exposed to the virus, there were 84% fewer cases of the disease compared to an unvaccinated group.
One potential factor that may have affected the effectiveness estimate is the HIV status of patients, as this information was not collected during the study. It is possible that individuals with compromised immune systems, such as those who are HIV-positive, may have had reduced protection from the vaccine. However, previous studies in monkeys infected with a simian equivalent of HIV showed that the vaccine offered solid protection.
Overall, the study highlights the importance of real-world assessments of vaccine effectiveness in challenging outbreak settings. Understanding how vaccines perform in these conditions can help improve outbreak response strategies and ultimately save lives. Vaccines play a crucial role in preventing the spread of infectious diseases, but they must be stored at specific temperatures before use to maintain their effectiveness. This can be a challenging task, especially in remote settings where electricity may be spotty. Without proper storage conditions, vaccines can lose their potency and become ineffective, putting communities at risk of outbreaks.
Dr. Sprecher, an expert in infectious diseases, emphasized the importance of maintaining cold chain storage for vaccines. He explained that vaccines with efficacy rates in the eighties or nineties are considered highly effective, even with just one dose. However, achieving these high efficacy rates requires strict adherence to temperature requirements during storage and transportation.
Dr. Feldmann, a virology expert, expressed some disappointment that the effectiveness estimate for a particular vaccine didn’t surpass 90%. However, he highlighted the significance of having an estimate that reflects real-world conditions, especially in outbreak settings. He emphasized that an efficacy rate of 85% or 84% is still very effective for managing outbreaks and preventing the spread of disease.
In remote settings where access to reliable electricity is limited, maintaining the cold chain for vaccines can be a major challenge. Without proper refrigeration, vaccines can quickly degrade and lose their effectiveness. This underscores the need for innovative solutions, such as solar-powered refrigeration units or temperature-stable vaccines, to ensure that vaccines remain potent even in challenging environments.
Overall, the importance of proper storage and temperature control for vaccines cannot be overstated. It is essential to invest in infrastructure and technology that can support cold chain storage in remote settings to ensure that vaccines reach communities in optimal condition. By addressing these challenges, we can enhance the effectiveness of vaccination programs and protect vulnerable populations from preventable diseases.
