Antibodies persist after 6 months

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New international research in the DRC reveals that the Ebola vaccine produces long-lasting protection. Kitsa Musayi/photo alliance via Getty Images
  • A new study looked at the antibody response in people who received the Ebola vaccine and live in areas of the Democratic Republic of Congo (DRC) that are experiencing outbreaks of Ebola virus disease.
  • Specifically, the researchers analyzed the antibody response at various time intervals after vaccination with a single dose of the Ebola vaccine in an at-risk population in the DRC.
  • They found compelling evidence of a robust and persistent antibody response in vaccinated people in affected areas.

the World Health Organization (WHO) defines Ebola virus disease (EVD) as a “rare but serious disease, often fatal in humans”.

Its symptoms usually include fever, fatigue, muscle aches, sore throat, and headache. Vomiting, diarrhea, and rash usually follow.

In some cases, EVD symptoms include internal and external bleeding, such as bloody stools or bleeding gums.

Currently, Ebola vaccines are part of an important scientific strategy to defeat EVD. Next to them are processing with drugs that the Food and Drug Administration (FDA) has approved and supportive therapy, such as oral rehydration and intravenous fluids.

A collaborative study between US and Congolese scientists recently examined the antibody response in people vaccinated against Ebola in the DRC, which is one of the first places scientists discovered EVD.

The study authors published their findings in the peer-reviewed journal Proceedings of the National Academy of Sciences.

The new study involved experts from the Fielding School of Public Health at the University of California, Los Angeles, in partnership with their colleagues in the DRC.

The team recruited a total of 608 participants between August and September 2018.

Scientists excluded children under 1 year old and pregnant or breastfeeding people,

Eligible study participants were contacts or “contacts of contacts” of confirmed EVD cases or frontline healthcare workers in areas affected or potentially affected by EVD.

During the enrollment period for the study, the Ebola vaccine — rVSVΔG-ZEBOV-GP – was not yet cleared by the FDA. As such, his administration was part of a compassionate use, also known as extended access, protocol process. In science, this is a situation in which a person with a serious or immediately life-threatening illness has access to an investigational medical product outside of a clinical trial.

During each study visit, scientists administered questionnaires to participants, performed basic physical assessment tests, and took blood samples.

The study visits for each participant took place at the following time intervals:

  • day 0, at least 30 minutes after vaccination and after monitoring for potential adverse effects
  • between day 21 and day 28 after vaccination
  • 6 months after vaccination

Overall, 58% of study participants were between the ages of 20 and 39 and 64% were male.

Of the participants, 32% reported having been in contact with a confirmed, probable or suspected case of EVD, while 66% reported no contact. The remaining 2% were unaware of their EVD contact history.

First, the scientists noted that study participants showed an increasing antibody response from day 0 up to 6 months after vaccination.

Additionally, they found that female participants were more likely to have a higher antibody response than their male counterparts at 6 months of follow-up.

Finally, the researchers observed significant differences in the antibody response between different age groups.

They noticed that the youngest participants, ages 12 to 19, had the highest antibody response at day 21 and 6 months after vaccination.

A possible explanation because the function of the immune system decreases with age. As a result, adolescents possess stronger immune systems that produce robust responses after vaccination.

Based on the above findings, the study authors write that their “results provide crucial evidence that antibody response and persistence after Ebola vaccination is robust in outbreak settings in the DRC.” They also note that this knowledge “significantly informs the use of vaccination for epidemic control.”

Responding to the findings of the study, Dr Monica Gandhiwho is a professor of medicine at the University of California, San Francisco and was not part of the study, said Medical News Today that the study was “exciting”.

“Although there were outbreaks of Ebola in the region at the time [of the study]the increase in antibody response over time suggests that the antibody response is vaccine-mediated, as the increase was consistent and suggested immune enhancement of the vaccine,” Dr. Gandhi explained.

“Given the mortality rate of Ebola, this is a very interesting study that shows the efficacy of this vaccine candidate in a large real-world study in a high-prevalence region.”

– Dr. Gandhi

The researchers acknowledge the limitations of their study.

They explain that they recruited a limited sample size with no defined control group due to resource constraints and security issues related to data collection in an active EVD outbreak area plagued by armed conflict.

Moreover, the authors point out that the correlates of protection remain undefined for EVD. Accordingly, it is not possible to use their discussion of the antibody response to draw conclusions regarding the protection afforded by vaccination.

Scientists define correlates of protection as the immune response that a vaccine or viral infection must trigger to protect an individual against the infectious disease in the future.

Regardless of these limitations, the researchers are now looking to future studies to build on the important foundation their research has laid.

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