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Shirin Ashraf, Emerging Diseases Postdoctoral Fellow, University of Glasgow
Arthur Wickenhagen, Ph.D. Candidate, MRC Virus Research Center, University of Glasgow
The World Health Organization (WHO) has pointed out that an experimental vaccine plays a major role in controlling the spread of the Ebola virus during the ongoing epidemic in the Democratic Republic of Congo (DRC). ). Without the vaccine, the epidemic risks becoming uncontrollable given the country's political and social context as well as the virus's ability to spread.
It is clear that the use of a vaccine at the beginning of an epidemic is an important step forward in the fight against this deadly disease. And yet, six months after diagnosis of the first case, the epidemic is still not controlled and cases are reported almost daily and sometimes spread outside.
By the end of January, 759 people had been infected. The death toll was 468, making it the second-worst epidemic ever recorded.
Normally, the DRC is well prepared and has extensive experience in combating the Ebola virus. However, a number of factors have impeded the current situation and made it difficult to control the epidemic, even for experienced medical teams at the borders.
The epicenter of the epidemic was in the province of North Kivu. This is in an area of active conflict and has very little infrastructure, which makes it very difficult to administer a sufficient amount of vaccine to ensure immunity. In addition, health workers have been confronted with widespread violent unrest due to political instability in the country. A number of units had to be removed as a result of attacks. Response rates were also slowed following demonstrations in the December elections.
The deployment of the vaccine
The rVSV-ZEBOV vaccine is being tested in the DRC. It was first deployed towards the end of the West Africa epidemic in Guinea in 2015. It was part of a phase III trial to evaluate the disease. Effectiveness of the vaccine to prevent the spread of Ebola among the population.
Initial survey data were obtained by comparing a group of vaccinated at-risk individuals immediately after diagnosis of a case of Ebola virus in their environment with a similar group of people who received the vaccine after a period of time. 21 days.
The "immediate" group did not contract the Ebola virus while some individuals in the delayed group contracted the disease. This evidence gave the WHO hope that the vaccine could be 100% effective.
But this point has not yet been reached. More data and surveys are needed before the vaccine is licensed for general use.
The deployment of the rvSV-ZEBOV virus in the DRC was achieved using a conventional strategy common in other vaccine trials. Called "ring vaccination", it involves vaccinating the first and second degree contacts of an infected individual. The goal is to form an immunized "ring" around each infection and prevent its subsequent transmission.
Since August 2018, nearly 66,000 doses of this experimental vaccine rVSV-ZEBOV have been administered in the DRC.
WHO's confidence in the vaccine was reinforced by the fact that the number of Ebola cases did not increase as much as that of 2014 in West Africa before the introduction of the vaccine.
But the effectiveness of vaccines is not always easy to evaluate. Detailed data from the current outbreak will help to make a more confident badessment and predict the future of its licenses and applications.
The vaccination landscape
Currently, WHO and the international community are supportive of the Merck rVSV-ZEBOV vaccine because it has already been used and a number of studies prove that it is a promising candidate for a license in the near future. In the current scenario, it is a glimmer of hope to face the current epidemic and prepare for the future. Merck recently promised to deploy 120,000 additional doses of vaccine in the DRC.
Other academic research on this vaccine has shown a sustained antibody response for two years, with little or no adverse health effects as part of a large multicenter study.
Besides the rVSV-ZEBOV, other potential vaccines are also under study. Two of them are under development by Johnson & Johnson and GlaxoSmithKline. The first tested a Prime-Boost vaccine, which is administered in two stages at different times; while the latter introduced a single-dose variant administered as a single injection.
Two other candidates come from China and Russia. The one in China has been approved by the country without testing or data on human efficacy, and that of Russia is also waiting for clinical trials. As a result, their safety and efficacy are still poorly understood and have not been used during these outbreaks.
The development of vaccines against difficult diseases such as the Ebola and Marburg viruses remains a very difficult task. The rate at which the rVSV-ZEBOV vaccine was developed and implemented, in addition to the effectiveness of the ring vaccination strategy, paved the way for future outbreaks.
However, the challenge is to reach a sufficient number of people vaccinated in unfavorable sociopolitical and underdeveloped infrastructure situations, such as those in many countries that are outbreaks of viral infection.
The burden of viral disease in Africa is largely underestimated and the rVSV-ZEBOV vaccine is, we hope, the first of many to be the subject of an accelerated follow up and to To invest in facing what is fast becoming a global health challenge. It is certainly an essential vaccine in the fight against the Ebola virus.
https: //theconversation.com/why-ebola-vaccine-on-trial-in-the-drc-is-rai …
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