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Smallpox and monkeypox vaccine (Imvamune)

Get protected, get immunized.

  • Vaccines make your immune system stronger. They build antibodies to help prevent diseases.
  • Immunization is safe. It's much safer to get immunized than to get this disease.

What is Imvamune?

Imvamune is a vaccine that protects against orthopoxvirus infections such as monkeypox and smallpox. As of the date at the bottom of this information, there are no cases of smallpox in Canada, but there are cases of monkeypox.

Imvamune is approved for use in Canada.

What is monkeypox?

Monkeypox is a rare disease caused by the monkeypox virus. It can infect humans. It’s usually mild and most people recover on their own after a few weeks. However, some people can get very sick and even die. Early symptoms may include:

  • fever
  • chills
  • swollen lymph nodes
  • headache
  • muscle pain
  • joint pain
  • back pain
  • exhaustion (feeling very tired)

Most people with monkeypox infection will get a rash or sores which can be on the hands, feet, mouth, and genitals. The rash can last 14 to 28 days. You can spread monkeypox to others from the time your symptoms start until the rash goes away and your skin heals. ​

Who is most at risk?

You’re at risk if you have close contact with someone who has monkeypox (for example, you live with the person or have sexual contact with them). You may be at higher risk of getting very sick if you:

  • have a weak immune system
  • are under age 18 years
  • are pregnant

How does it spread?

Monkeypox spreads through close contact with someone who has monkeypox. It may also spread if you have contact with bedding, sheets, or clothing that touches the rash and has virus on it. The virus enters the body through broken skin or your eyes, nose, or mouth.​

How can I prevent monkeypox from spreading?

Here’s what you can do to prevent monkeypox from spreading:

  • Wash your hands with warm water and soap or use an alcohol-based hand sanitizer often.
  • Don’t touch your face, nose, or mouth with unwashed hands.
  • Cover your cough or sneeze into your arm or a tissue, not your hand.
  • Stay home when you’re sick or have skin sores.
  • Practise safer sex (use condoms or other barriers against skin-to-skin contact).
  • Avoid close contact with people who have monkeypox and their clothing, towels, or bedding.

Who should get Imvamune?

You may be able to get this vaccine if you are age 18 years or older and have a higher risk of being exposed to monkeypox. You may have a higher risk if you belong to the gay, bisexual, or men who have sex with men (gbMSM) community and:

  • You have more than one sexual partner.
  • You attend or work at places where people may have sexual or skin-to-skin contact with more than one partner (such as bath houses, sex clubs, or sex parties).
  • You have had a sexually transmitted infection in the last 6 months.

If you have or are planning on having sexual contact with someone who could be at higher risk, you may also be able to get this vaccine.

You should also get this vaccine if you had close contact with someone who has monkeypox. It's best to get this vaccine within 4 days of close contact, but you can get it up to 14 days after. Once your symptoms start, you can no longer get the vaccine.

Call Health Link at 811 to find out if you should get this vaccine.

Imvamune is licensed for people age 18 years or older. However, vaccine experts support using Imvamune for people of any age who have close contact with someone who has monkeypox. If you get the vaccine and are under age 18 years, this is called “off-label use.” There is limited information on the use of Imvamune in children. Studies done with similar vaccines show there were no safety concerns for children under age 18 years.  Talk to your healthcare provider if you are under age 18 years before getting this vaccine.

How many doses do I need?

You need at least 1 dose. ​​​​​You may need a second dose at a later date for long-term protection or if you get exposed to monkeypox virus. Talk to your healthcare provider about how many doses you need.

How well does the vaccine work?

For Imvamune to work, you need to get it before monkeypox symptoms start. If you get Imvamune after contact with monkeypox virus, the vaccine can protect you from getting a monkeypox infection, or it can make the infection milder. If you have a weak immune system, the vaccine may not work as well.

Where can I get Imvamune?

If you think you may be at higher risk for being exposed to monkeypox, call Health Link at 811 to see if you can get the vaccine.

Public Health will contact you if you are identified as a close contact of a confirmed case of monkeypox. If Public Health decides that you need Imvamune, they will tell you where to go for the vaccine.

Are there side effects from Imvamune?

There can be side effects from Imvamune, but they tend to be mild to moderate and go away within 7 days. Side effects may include:

  • at the area where you had the needle: redness, changes in skin colour, bruising, swelling, warmth, itching, a hard spot or small lump, or feeling sore
  • feeling tired
  • a headache
  • a fever or chills
  • body aches, sore joints
  • pain in your arms or legs
  • not feeling hungry or not wanting to eat (poor appetite)
  • feeling sick to your stomach (nausea)

It’s important to stay at the clinic for 15 minutes after your vaccine. Some people may have a rare but serious allergic reaction called anaphylaxis. If anaphylaxis happens, you’ll get medicine to treat the symptoms.

It’s rare to have a serious side effect. Call Health Link at 811 to report any serious or unusual side effects.

What rare events have been reported after getting Imvamune?

There have been rare reports of cardiac (heart) symptoms after getting Imvamune. However, none were considered serious. There have also been reports of myopericarditis (an inflammation of both the heart muscle and lining around the heart) after other vaccines that protect against smallpox. However, no cases of myopericarditis after Imvamune have been reported. Get medical help right away if you have any of these symptoms:

  • shortness of breath
  • chest pain
  • a fluttering feeling in your chest (palpitations)

It is not known if having a history of myocarditis (inflammation of the heart muscle) or pericarditis (inflammation of the lining around the heart) after getting Imvamune or another smallpox vaccine puts you at higher risk of having these rare events. Talk to your healthcare provider before getting Imvamune if you have had these rare events after getting a smallpox vaccine or Imvamune.

How can I manage side effects?

To help with soreness and swelling, put a cool, wet cloth over the area where you had the needle.

There is medicine to help with a fever or pain. Check with your doctor or pharmacist if you’re not sure what medicine or dose to take. Follow the directions on the package.

Children under the age of 18 years should not take aspirin (unless your doctor has told you to take it) because it can cause serious health problems if taken within 6 weeks of a vaccine.

Some people with health problems, such as a weak immune system, must call their doctor if they get a fever. If you’ve been told to do this, call your doctor even if you think the fever is from the vaccine.

What if I had or am getting another type of vaccine?

It’s best not to get Imvamune at the same time as another vaccine.

If you got another vaccine in the last 14 days, talk to your healthcare provider about when you should get Imvamune.

After getting Imvamune, you should wait at least:

  • 4 weeks before getting a COVID-19 mRNA vaccine
  • 14 days before getting any other vaccine

Who should not get Imvamune?

You may not be able to get this vaccine if you:

  • have an allergy to any part of the vaccine
  • had a serious or unusual side effect after this vaccine or one like it

Check with your doctor or a public health nurse before you get Imvamune.

You can still get the vaccine if you have a mild illness such as a cold or fever. You can get the vaccine if you have eczema (atopic dermatitis—a skin condition that makes your skin red and itchy). People with eczema are more likely to have serious side effects with other smallpox vaccines, but this has not been reported with Imvamune. If you have eczema and get Imvamune, you may be more likely to have common vaccine side effects or your eczema could get worse. Talk to your healthcare provider if you have questions.

There is more to learn about Imvamune and certain groups of people. Talk to your healthcare provider before you get Imvamune if you:

  • have a weak immune system (because of medicine you take or a ​health problem)
  • are pregnant or breastfeeding
  • are under age 18 years
  • have a history of myocarditis or pericarditis after getting smallpox vaccine or Imvamune

I have a fear of needles. How can I prepare for my immunization?

Many adults and children are afraid of needles. You can do many things before, during, and after immunization to be more comfortable. Visit Commitment to Comfort​ for tips to make immunization a better experience.

For more information about immunization

Current as of: August 11, 2022

Author: Provincial Immunization Program, Alberta Health Services