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Study on the Congo epidemic: Ebola seems to be highly effective – knowledge



He has not yet been accepted and yet has saved countless lives: rVSV-ZEBOV appears to be highly effective against the deadly Ebola virus. This is confirmed by new studies in which researchers analyzed the use of the vaccine in the event of a disease outbreak in the Democratic Republic of Congo.

The experimental vaccine was used as early as 2014 at the end of the devastating Ebola epidemic in West Africa, killing 11,000 people after proving very good protection in animal experiments. Anyone who received it at that time was spared Ebola. When a disease broke out in northwestern Congo last April, WHO decided to use rVSV-ZEBOV again.


Rapid and coordinated interventions made it possible to quickly stop the focus. 54 cases became known, 33 people died. It was announced in July. Researchers led by Chad Wells of the Yale School of Public Health report in the PNAS newspaper that rapid success in northwestern Congo is largely due to the fact that vaccination started only two weeks after the outbreak was announced.

Circular vaccination as an important factor

Wells and his colleagues looked at how fast vaccination had affected the risk of infection. To do so, scientists combined the factors of poverty, density and mobility of the population and compared the model with the scenario without a vaccination campaign.

According to her calculations, vaccination has reduced both the geographical area at risk of Ebola infection and the probability of transmission by more than 70 percent. "If the vaccine started only a week later, the risky area would be reduced by just 33 percent and the general probability of infection by only 45 percent," scientists say.

An important factor was also the way in which the vaccine was used: ring inoculation. Healthcare professionals identify contact persons of people who are infected with Ebola and those who come into contact with them. Nearly 3,800 of these primary and secondary contacts (circles around patients, so-called) were immediately vaccinated in spring 2018. None of these people were subsequently infected with Ebola. The researchers concluded that a rapid and coordinated response after the outbreak was necessary to limit it.

More than 90,000 vaccinations since August 2018

However, this rapid response is not possible in the Congolese provinces of North Kivu and Ituri. There the virus rages from August 2018 and is still not under control. According to the World Health Organization (WHO), more than 1,400 people have already had a fever and 931 have died by 27 April 2019. The armed conflict is raging in the region in the east of the country, with frequent attacks on helpers and treatment centers. Healthcare professionals do not have access to many villages, so it is difficult to track illnesses and their contacts.

But even though the conditions are catastrophic in many places, probably without a vaccine, many more people would die on Ebola. This is stated in the WHO Preliminary Report and the National Research Institute of the Democratic Republic of Congo (PDF) from 1 August 2018 to 25 March 2019.

More than 90,000 people were vaccinated against Ebola during this period. To assess the efficacy of the vaccine, scientists evaluated the number of disease in the patient's contact persons and compared it to the risks of non-vaccination. Of this, 97.5 percent had a very good vaccination efficiency.

Effective protection only after ten days

It was previously thought that the vaccine needed about ten days to be effective. This was confirmed in the study. Of the 57 people who developed Ebola symptoms within 10 days of vaccination, nine died. In contrast, all 15 vaccinated survivors, which occurred at the earliest after ten days, of Ebola's symptoms.

In addition, the vaccine even increases the likelihood of survival of already infected persons. This is especially important because there is still no approved treatment for Ebola.

Although researchers recognize that their analysis is merely an observational study that could lead to bias. However, the preliminary assessment suggests that the vaccine could be as effective as anticipated after the first studies.

As a result of the Ebola outbreak in West Africa in 2013, the WHO ordered studies to test potential vaccine candidates. The most promising vaccine is rVSV-ZEBOV. It is a live vaccine developed in 2003 by scientists from the National Microbiological Laboratory in Winnipeg, Canada. At that time, at the time of the Ebola outbreak in West Africa, he was already the most advanced in his testing. The latest data seems to confirm the choice of vaccination. Researchers will soon publish their results in a journal.

To protect them, you have to reach people

Despite this positive report, the reality in Congo is still different. The number of Ebola infections is still high, although slightly lower after the end of March. The virus has not spread to neighboring countries yet, but the possibility remains.

In mid-April, the WHO announced that the Congo epidemic is not a global health crisis. As a result, MSF called for a "better joint effort" against the epidemic. "We need to radically change the way we approach it," said Gwenola Seroux, Ebola Emergency Response Director. It is necessary to integrate measures against disease into the local health system and to work better with the local population.

In its latest report on the situation in the Congo, the WHO also writes that there is a need for social engagement to prevent further attacks on helpers and health professionals. To protect people with Ebola vaccines, you must first achieve them.

So there are many more. And yet, new data gives hope. I hope that one dose of the vaccine can be an effective means for the Ebola epidemic. If you find and track patients' contact persons. Since the situation is different: The circular vaccination method was used very successfully before: in smallpox eradication.


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