While the Ebola outbreak is raging, the vaccine is 97.5% effective and protects over 90,000 people

An experimental vaccine against the Ebola virus is 97.5% effective in preventing this disease, protecting well over 90,000 people during the massive and persistent epidemic in the Democratic Republic of Congo, according to preliminary data.

The outbreak has erupted since last August, involving 1,264 cases (1,198 confirmed, 66 probable) and 814 deaths (748 confirmed, 66 probable), making it the second largest outbreak of Ebola recorded. Until now, the epidemic has remained in the provinces of North Kivu and Ituri in the DRC, located in the east of the country, on the border with South Sudan, Uganda and Rwanda. But intervention efforts have been severely compromised by community mistrust of public health campaigns. As a result of this mistrust, several activists attacked medical facilities, wounded medical staff and, in one case, killed a police officer. Some public health experts fear that the epidemic will continue to spread without new strategies and increased help, possibly across neighboring borders.

Nevertheless, the epidemic could have been much worse without an experimental vaccine. The rVSV-ZEBOV-GP Ebola vaccine, manufactured by Merck & Co, contains an attenuated live virus that is harmless to humans that researchers have genetically engineered to contain an Ebola glycoprotein. Ebola usually uses this protein to interact with human cells, but in the vaccine, the human immune system is led to generate powerful antibodies to attack the virus. The first tests of the vaccine seemed to confirm it, suggesting that it was safe and effective. And a strategic advisory group of experts from the World Health Organization (SAGE) gave stakeholders the green light to use the vaccine during epidemics, based on a protocol extended access / compassionate use.

As in the last epidemic, health workers are currently releasing it as part of a targeted immunization strategy, which aims to vaccinate people in contact with known cases of Ebola and to contacts in the community. these contacts, creating social networks of vaccination to protect the most vulnerable and prevent the spread of the virus. disease. It was the same vaccination strategy as that used for the eradication of smallpox, the only human disease to have been totally eliminated. Although the Ebola virus spreads from animals – so it could not be eliminated from a single human vaccination campaign – the strategy is considered the most effective way to quickly and effectively extinguish outbreaks and epidemics.

This appears to be the case in the current outbreak, according to preliminary data released by researchers from the WHO and DRC (PDF). Between August 1, 2018 and March 25, health stakeholders identified 679 rings in approximately 776 of the 951 confirmed and probable cases during this period. They vaccinated nearly 94,000 people, including nearly 29,000 health care workers and frontline workers during this period (more of them have since been vaccinated).

Of those vaccinated, only 71 people contracted the Ebola virus. Most of these cases (54 out of 71) had high-risk contacts – those who would have the best chance of contracting the virus due to exposure. In addition, most of them (56 out of 71) occurred within 10 days of immunization, before the vaccine gave full protection. Fifteen of the estimated 94,000 people vaccinated became ill after this ten day period and all survived the infection, which usually has a mortality rate of about 50%.

By examining the rings as a whole, the researchers found that the Ebola virus could cross only about 9% of the rings vaccinated (60/679 rings), and that only about 2% of these rings included cases after the 10-year period. days. Finally, of the 68,279 vaccinated individuals identified as "contact contacts", only two vaccinated persons contracted the virus. This suggests that the vaccine and the vaccination strategy were very effective in preventing the spread of the disease.

In total, based on calculations comparing the spread of the Ebola virus by vaccinated and unvaccinated rings, the researchers estimated that the virus attack rate was 0.017% among vaccinated and 0.656% among non-vaccinated . This gives an estimated efficiency rate of 97.5%.

At a meeting at the end of last week, WHO experts assessed the epidemic as a whole and determined that it was not an "important public health emergency". although they have expressed "deep concern" about the continued spread of the virus. They called for continued immunization and redoubled efforts to work with communities to eliminate the disease.