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Study of Different Doses of MVA-BN Vaccine Booster for Adults with Mpox: Comparing Standard and Reduced Doses

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on mpox (formerly known as monkeypox) and investigates the effectiveness of booster vaccinations using IMVANEX, which contains Modified Vaccinia Ankara virus. The vaccine is given as an injection under the skin (subcutaneous injection), and the study compares two different doses of the same vaccine - a standard dose and a reduced dose.

The purpose of this research is to determine if a smaller dose of the vaccine can provide the same level of protection against mpox virus as the standard dose when given as a booster shot. The vaccine contains a modified form of the vaccinia virus that has been altered to be safe while still helping the body develop protection against mpox.

During the study, participants will receive one booster dose of the vaccine and will be monitored for six months. The study will measure the body's immune response by checking for protective substances (antibodies) in the blood. Healthcare providers will also track any reactions or side effects that may occur after vaccination. Blood samples will be collected at specific times to measure how well the vaccine is working.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

Step 1
Initial vaccination visit
You will receive a booster vaccination of IMVANEX through a subcutaneous injection (under the skin).
The vaccine contains modified vaccinia virus to protect against mpox infection.
You will be assigned to receive either a standard or reduced dose of the vaccine.
Step 2
7-day monitoring period
You will need to complete an electronic diary for 7 days after vaccination.
The diary will track any local reactions (such as injection site reactions) and systemic reactions (such as fever).
Continue recording symptoms until they resolve, even if longer than 7 days.
Step 3
14-day follow-up visit
You will attend a follow-up visit 2 weeks after vaccination.
Blood samples will be taken to measure your body's immune response to the vaccine.
Your vaccination site will be examined and any side effects will be reviewed.
Step 4
6-month follow-up visit
A final visit will occur 6 months after your vaccination.
Additional blood samples will be collected to check your long-term immune response.
Any serious side effects that occurred during the study period will be reviewed.
Step 5
Study completion
The study will end after your 6-month follow-up visit.
Your participation helps evaluate if a reduced vaccine dose provides similar protection against mpox virus compared to the standard dose.

Who can join the trial?

8 criteria

Must be 18 years or older at the time of providing consent
Must be able to give personal signed consent and follow study requirements
Must be born after 1974 and have received two doses of MVA-BN vaccine at least one year before joining the study
Must be generally healthy. People with stable pre-existing conditions can participate if their condition has not required significant treatment changes or hospital stays in the 6 weeks before enrollment
Must be willing and able to attend all scheduled visits, follow the vaccination schedule, complete laboratory tests, and comply with other study procedures
For participants who can become pregnant (have a uterus and are not surgically sterilized or post-menopausal):
- Must not be pregnant or breastfeeding
- Must agree to pregnancy testing
- Must use effective birth control for at least 4 weeks after the third MVA-BN vaccination

Who cannot join the trial?

13 criteria

Age below 18 years or above 64 years old
Previous diagnosis of mpox infection (formerly known as monkeypox)
Currently pregnant or breastfeeding women
Known allergic reactions to any components of the MVA-BN vaccine
Participation in other clinical trials within the past 30 days
Active infection or fever above 38°C (100.4°F) at the time of vaccination
Weakened immune system due to medical conditions or medications
History of severe allergic reactions to vaccines
Recent receipt of any other vaccine within 14 days
Current use of blood thinners or bleeding disorders
Any serious chronic medical condition that is not well controlled
Unable to complete all required study visits
Previous vaccination with any smallpox or mpox vaccine

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Verified sites

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Leids Universitair Medisch Centrum (LUMC)
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Leiden, The Netherlands

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Investigated drugs

MVA-BN (Modified Vaccinia Ankara - Bavarian Nordic) is a vaccine designed to protect against mpox (formerly known as monkeypox). It is a live, modified form of the vaccinia virus that has been adapted to be safer while still providing immunity. The vaccine is administered through subcutaneous injection (under the skin) and is used as a booster vaccination to enhance immune protection in people who have previously received an initial dose. This vaccine helps the body create antibodies to fight against the mpox virus.

Modified Vaccinia Ankara – Bavarian Nordic Live Virus

What is already known about the treatment

MVA-BN - A specialized vaccine administered subcutaneously (under the skin) for the prevention of mpox (formerly known as monkeypox). This modified vaccinia Ankara-Bavarian Nordic vaccine belongs to the class of live attenuated vaccines and works by stimulating the immune system to produce antibodies against the mpox virus. The vaccine has been clinically tested in various dosing regimens, including fractional doses as booster shots, and has shown promising results in providing protection against mpox infection. Currently, it represents one of the primary preventive measures available in modern medicine for mpox control and is being studied to optimize its dosing strategy for booster vaccinations.

Investigated diseases

Mpox - A viral disease caused by the monkeypox virus that affects humans. The condition typically begins with flu-like symptoms including fever, headache, and muscle aches. After the initial symptoms, a characteristic rash develops, which progresses from flat spots to raised bumps, then to fluid-filled blisters that eventually scab over. The rash commonly appears on the face, hands, feet, and other parts of the body. The illness usually lasts between 2-4 weeks, with symptoms generally appearing within 1-2 weeks after exposure.