Ongoing, recruitingTherapeutic use (Phase IV)Interventional

(The Lion Trial) LAIV induced Immune respOnse in the Nasopharynx

The Lion Trial aims to understand how the Fluenz nasal spray flu vaccine, a live attenuated influenza vaccine (LAIV), protects people from flu. Researchers are specifically looking at how the vaccine virus spreads in the nose after someone has had the spray, and how long it stays there. They're also examining the body's immune response in the nose, including changes in antibodies and other protective substances. This study will help us understand better how this type of flu vaccine works in real-world use.

At a glance

Status

Ongoing, recruiting

Phase

Therapeutic use (Phase IV)

Sponsor

Leids Universitair Medisch Centrum (LUMC)

Enrolment target

Start

24 Jul 2025

Influenza

What is this study about?

The Lion Trial is a study focused on a specific type of flu vaccine that's given as a nasal spray, often known by its brand name, Fluenz. This vaccine uses a weakened, but live, version of the flu virus to help your body build protection against the actual flu. The main goal of this study is to see if, after you've had the nasal spray vaccine, tiny amounts of this weakened vaccine virus are present in the lining of your nose. They want to know if it's there after the first dose and again after a second dose.

Researchers will collect samples from the inside of people's noses to check for this vaccine virus. They'll also be looking closely at how your body's immune system reacts. This includes measuring protective substances called antibodies in your nose, and seeing how other immune responses change after vaccination. This helps scientists understand how well your body learns to fight off the flu after getting the nasal spray.

Beyond just the flu vaccine itself, the study will also look at how other common germs in your nose and throat might change after vaccination. They will even check your blood to understand your body's overall immune response. All this information will help doctors understand more about how the nasal spray flu vaccine works and how effective it is in protecting people from the flu.

Key takeaways

The study investigates how the Fluenz nasal spray flu vaccine works.
It checks for the vaccine virus in the nose after vaccination.
Researchers will also measure the body's immune response in the nose and blood.
It aims to improve our understanding of how this specific flu vaccine protects against flu.
Participation involves nasal samples, blood tests, and symptom questionnaires.

Who may be eligible?

This study is open to both adults and children, of any age. It includes people of all genders. The raw information didn't specify any other restrictions at all, but usually, studies have other things they consider when deciding who can take part.

For example, doctors might consider your general health to make sure the study is right for you. They’ll also check to see if you've already had certain illnesses or medications that might affect the study results. Because this is a flu vaccine study, they will ensure you haven't recently had a flu shot or the flu itself.

Always discuss your full medical history with the study team to make sure it's safe for you to take part and that you meet all the necessary requirements.

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.

Am I open to receiving the Fluenz nasal spray flu vaccine?
Am I able to provide samples from the inside of my nose?
Am I comfortable with having blood samples taken?
Can I complete daily questionnaires about my health?
Do I fit the age and gender requirements mentioned by the study team?

Answer every question to see your result.

What does participation involve?

If you decide to take part in this study, you would receive the Fluenz nasal spray flu vaccine. The researchers will collect samples from the lining of your nose multiple times after you get the vaccine. This is done with a special device called a 'nasosorption' which gently collects fluid from your nose. You will also be asked to complete questionnaires, possibly electronic ones, each day about any cold or flu-like symptoms you might have. At the beginning of the study and 28 days after your first vaccine dose, blood samples will be taken. We don't have a specific total duration for this study, but given the follow-up, it would likely involve several visits over a few weeks or months.

Potential risks and benefits

Taking part in a study like this helps improve our understanding of flu vaccines and could lead to better public health. You might experience minor side effects from the nasal spray vaccine, similar to those you'd get from a regular flu jab, such as a runny nose, feeling a bit under the weather, or a sore throat. There's also some discomfort from the nasal samples and blood tests. You are free to withdraw from the study at any time, for any reason, without it affecting your medical care.

Locations (1)

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

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Unverified
Netherlands

Common questions

What is the main purpose of The Lion Trial?

The study wants to understand how the Fluenz nasal spray flu vaccine works in your nose and how your body's immune system reacts to it.

What is Fluenz?

Fluenz is a nasal spray flu vaccine that uses a weakened form of the flu virus to protect you from getting sick.

What kind of samples will be collected?

Researchers will collect samples from the lining of your nose and some blood samples to check for the vaccine virus and measure your immune response.

Is this a new vaccine?

No, Fluenz is an approved flu vaccine. This study is looking at how it works in more detail after it has been used for some time (this is called Phase IV research).

Will I have to fill out questionnaires?

Yes, you will be asked to complete daily questionnaires about any cold or flu-like symptoms you experience during the study.