Measles: Prevention and risks
On this page
- How measles spreads
- Preventing measles with vaccination
- Prevention after exposure to measles
- Who is most at risk
How measles spreads
Measles is a viral infection. If you're infected, you can spread measles from 4 days before the onset of the rash until 4 days after the rash appears. The measles virus can live up to 2 hours in the air or on surfaces in a space where you've been.
You can become infected with the measles virus when you:
- breathe in air containing infectious respiratory particles, such as in a location where someone who's infected with measles is or has recently been
- have direct contact with secretions (for example, mucus) from the nose or throat of someone who's infected
- touch a contaminated surface or object and then touch your eyes, nose or mouth before cleaning your hands
Measles is very contagious and can easily spread to those who aren't immune. These are people who aren't vaccinated or haven't been previously infected with the virus.
Overall, Canada generally has high vaccination rates against measles but there are communities and regions where vaccination rates are low. Measles cases and outbreaks still happen in Canada, as measles is present worldwide and travellers who aren't vaccinated can bring measles into Canada.
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Preventing measles with vaccination
There are 2 kinds of measles-containing vaccines in Canada, and both also offer protection against other illnesses. They are the:
- measles-mumps-rubella (MMR) vaccine
- measles-mumps-rubella-varicella (MMRV) vaccine
- varicella is also called chickenpox
The first dose of a measles-containing vaccine is usually given to children at 12 months of age.
The second dose of a measles-containing vaccine is usually given to children at 18 months of age or 4 to 6 years of age.
One dose of a measles-containing vaccine given after 12 months of age is up to 95% effective at preventing measles. Having 2 doses is about 99% effective.
Vaccination schedules vary depending on your province or territory.
Adults born before 1970
If you were born before 1970, you're presumed to have immunity as it's likely you were infected with the measles virus when you were younger. However, 1 or 2 doses of a measles-containing vaccine may be recommended if you are:
- a health care provider
- travelling internationally
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Adults born in or after 1970
Adults born in or after 1970 are recommended to receive at least 1 dose of a measles-containing vaccine.
For some adults born in or after 1970, 2 doses of a measles-containing vaccine are recommended for:
- health care workers
- those who are travelling internationally
- those who attend post-secondary education, such as college or university
Talk to a health care provider to make sure you have had all the measles-containing vaccine doses recommended for you.
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People who are pregnant or immunocompromised
People who are pregnant or immunocompromised (have a weakened immune system) are generally not recommended to receive a measles-containing vaccine. However, they should consult with a health care provider if they're not previously vaccinated and are at risk of exposure to measles.
Safety of measles-containing vaccines
After vaccination, it's common to have mild side effects at the site where the vaccine was given, including swelling, soreness and redness.
Within 1 to 3 weeks after vaccination, some people may develop 1 or more of the following:
- fever
- mild rash
- temporary joint pain or stiffness
- swelling of the neck lymph nodes
- swelling of the glands of the cheeks
These reactions are normal and usually go away within a few days. You can take medication if needed for pain or fever. Check with a health care provider if you have any concerns or need advice about which medication to use.
Very rarely, someone may have a serious reaction to a vaccine, including an allergic reaction. Symptoms of a serious allergic reaction typically happen soon after vaccination and can include:
- breathing problems (wheezing)
- swelling of the face, tongue or throat
- red bumps on the skin that are often itchy (hives)
If you suspect you might be having a serious reaction after a vaccination, seek medical care right away. Serious side effects from vaccines should also be reported to your local public health unit. Tell a health care provider about any serious reactions you've experienced before you receive future vaccinations.
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Prevention after exposure to measles
If you think you've been exposed to someone with measles, talk to a health care provider. They'll provide advice on how to reduce your risk of infection, especially if:
- you're not vaccinated against measles
- you haven't been previously infected with measles
They may recommend the measles vaccine or a medication that contains protective antibodies. These should be given as soon as possible after exposure.
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Who is most at risk
You're more likely to become infected if you're:
- unvaccinated and haven't previously had a measles infection and
- travelling to regions or countries where measles is circulating
Travellers who become infected abroad may bring measles back to Canada. This can cause spread in the community, particularly if many people are unvaccinated or not fully vaccinated.
Some people are at higher risk of developing severe complications from measles, including:
- people who are pregnant
- people with weakened immune systems
- children who are less than 5 years of age
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