Using ribavirin to treat Lassa fever might not be backed up by evidence

Researchers from the Universities of Bristol and Oxford, funded by the World Health Organization (WHO) and by the NIHR Bristol BRC, found that there was only limited evidence to support using ribavirin, an antiviral medication, to treat patients diagnosed with Lassa fever. Ribavirin has been used to treat Lassa fever in West Africa since the 1980s, but researchers found that only a few studies have so far tried to assess how effective it is in treating this disease.

The Lassa virus is a priority pathogen according to the WHO. This is because of its epidemic potential, its severity, the lack of available vaccines and limited treatment options. Lassa fever has a significant impact on the health system in West Africa because that is where the majority of the estimated 100,000 to 200,000 cases develop each year.

Researchers identified 13 studies comparing the effectiveness of treatment with ribavirin to treatment without it. They looked at how this affected the number of patients dying from the disease. This included looking at additional unpublished data from a study in Sierra Leone provided after a Freedom of Information request by Prof. Sir Peter Horby and the Oxford Team.

The research team reviewed the selected studies and found that, although ribavirin treatment was generally associated with fewer patient deaths, almost all the study results were at risk of being affected by bias. This meant that their results could have been skewed by errors that were inadvertently introduced into the studies. Such biases make it difficult to evaluate how effective ribavirin really is in clinical practice.

The most influential study assessing the effectiveness of ribavirin on Lassa fever was published in 1986. It reported that administering intravenous ribavirin within the first six days of illness decreased mortality from severe Lassa fever from 55% to 5%. However, additional unpublished data from that study called the strength of these conclusions into question.

Hung-Yuan (Vincent) Cheng, a researcher working on the project, said:

“We were glad to have infectious disease experts – Dr Alex Salam and Prof Sir Peter Horby from the University of Oxford – involved in this review to provide their clinical expertise and thoughts on the topic.

“We were all shocked by the amount of evidence that had supported practice over the past 25 years. Sometimes even common practice should be taken with a pinch of salt.

“We’re excited to see how evidence supports practice in relation to other diseases and guidelines in the future.”

Jonathan Sterne, study lead, said:

“We need well-conducted clinical trials to assess if ribavirin is effective in the treatment of Lassa fever.

“Current treatment guidelines don’t highlight the weakness of the primary evidence.”