CompletedInterventional

VITAL01: A study of a new vaccine against Lassa fever in adults aged 18-55 years

This study is looking for healthy adults, aged 18 to 55, to test a new vaccine against Lassa fever. Lassa fever is a virus common in West Africa, spread by rodents. While many cases are mild, it can be very serious, especially for pregnant women, and can cause long-term problems like hearing loss. Currently, there's no vaccine or specific treatment. The study aims to find out if the new vaccine, called ChAdOx1 LassaJ, is safe and how well it helps your body create protection against the virus. Participants will receive either the vaccine or a dummy shot, and your health will be closely monitored. Taking part helps researchers develop a much-needed vaccine, though you won't get direct personal health benefits from this study.

At a glance

Status

Completed

Sponsor

University of Oxford

Enrolment target

Start

05 Nov 2025

Estimated completion

31 Mar 2026

Lassa virus

What is this study about?

Lassa fever is an illness caused by a virus that is usually carried by rodents, like rats. Around 60 million people in West Africa are at risk of catching it every year. For most people, the illness might be mild, but it can become very severe and even deadly, especially for pregnant women and their unborn babies. People who recover from Lassa fever can sometimes have ongoing problems, such as hearing loss or issues with their balance.

Because there is currently no special medicine to treat Lassa fever and no vaccine to prevent it, scientists are working hard to find ways to protect people. The Oxford Vaccine Group is running this study to test a brand new vaccine called ChAdOx1 LassaJ. This will be the very first time this vaccine is given to people, and the main goal is to check how safe it is and how well it helps your body create an immune response, which is your body's way of fighting off illness.

By taking part in this study, you would be helping us learn more about this promising new vaccine. Your involvement is incredibly important for developing a way to protect people from Lassa fever in the future.

Key takeaways

Tests a new Lassa fever vaccine for the first time in people.
Aimed at healthy adults aged 18-55.
Checks vaccine safety and how well your body builds protection.
Involves two doses (vaccine or dummy shot) 12 weeks apart.
Possible side effects are usually mild and temporary, but severe rare effects have been seen with similar vaccines.
Your contribution helps develop a vital vaccine for global health.

Who may be eligible?

This study is looking for healthy adults between 18 and 55 years old. You need to be generally well and not expecting to stay in hospital for anything unrelated to the study during the trial period. You should also be able to come to all the planned appointments and follow the study instructions, including using an online diary.

You'll need to agree to share your medical history, either by providing medical documents or allowing the study team to get them from your GP. We'll also need your permission to let your GP know you're in the study. You'll be asked to provide your National Insurance number or passport number to an online system that checks if people are taking part in too many studies at once.

If you could become pregnant, you'll need to use effective birth control throughout the study and have pregnancy tests at certain times. We also can't include you if you've recently taken part in another research study that might affect this one, such as having a lot of blood taken, or if you're planning to do so.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

Are you between 18 and 55 years old?
Are you generally healthy and not in hospital often?
Can you commit to attending all study appointments at Oxford?
Are you willing to share your medical history with the study team?
If you can become pregnant, are you willing to use effective birth control during the study?

Answer every question to see your result.

What does participation involve?

If you join the study, you'll be put into one of two groups. One group will get the new Lassa fever vaccine, and the other group will get a dummy injection (placebo). You won't know which one you receive. You'll get two injections, 12 weeks apart.

The study will involve several visits to the clinic over a period of time, from June 2024 to September 2027. You'll have various check-ups, and we'll take blood samples to see how your body is responding to the vaccine or placebo. You'll also need to keep an electronic diary. We'll also check your hearing at the beginning and end of the study.

Potential risks and benefits

By taking part, you'll be making a very important contribution to developing a safe and effective vaccine against Lassa fever, which could protect many people in the future. However, you won't personally receive any direct health benefits from this study. Like all medicines and vaccines, there can be side effects. The most common ones for this type of vaccine include temporary soreness or pain where you had the injection, feeling tired, a headache, generally unwell, or a bit feverish. These usually go away within a few days. Very rarely, similar vaccines have been linked to serious side effects like certain blood clots or nerve problems. While it's unknown if these would happen with this specific vaccine, we will tell you about them, and the study team will be looking out for any signs. You are free to withdraw from the study at any time for any reason, without it affecting your medical care.

Locations (2)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

Oxford Vaccine Group, University of Oxford
City only
Oxford, England
Oxford University Hospitals NHS Foundation Trust
City only
Oxford, England

Common questions

What is Lassa fever?

Lassa fever is a viral illness found in West Africa, spread by rodents, which can be mild or very serious and lead to long-term health issues.

Who can join this study?

Healthy adults aged 18 to 55 years old who are able to attend all study appointments and follow instructions.

What will I receive in the study?

You'll receive two doses, 12 weeks apart, of either the new Lassa fever vaccine or a dummy injection (placebo).

Will I get any personal health benefits?

While you won't get direct personal health benefits, your participation is vital in helping to develop a much-needed vaccine for Lassa fever.

Where is the study happening?

The study is being run from the University of Oxford in the UK.

How to find out more

Reyna Sara Quintero Barceinas

sara.quinterobarceinas@paediatrics.ox.ac.uk - Official trial record

Always speak to your GP or specialist before deciding to take part in a study.