Measles: Prevention and risks

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How measles spreads

The measles virus spreads when you:

  • breathe air in a location where someone who's infected is or has recently been
  • have direct contact with 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

If you're infected, you can spread measles from 4 days before the onset of a rash to 4 days after a rash appears. The measles virus can live up to 2 hours in the air or on surfaces in a space where you've been.

Measles is very contagious. Over 90% of people who aren't immune to measles and who come into contact with the virus will become infected.

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 may bring measles into Canada.

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Preventing measles with vaccination

Having 2 doses of a measles-containing vaccine after 1 year of age is almost 100% effective at preventing measles.

There are 2 kinds of measles-containing vaccines in Canada, which also contain vaccines for other illnesses. They are:

  1. measles-mumps-rubella (MMR)
  2. measles-mumps-rubella-varicella (MMRV)

The first dose of a measles-containing vaccine is usually given to children when they're between 12 and 15 months old.

The second dose of a measles-containing vaccine is usually given to children at 18 months of age or before they enter school.

Vaccination schedules may vary depending on your province or territory.

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Adults born before 1970

If you were born before 1970, you're presumed to have immunity as it's likely you came into contact with the measles virus when you were younger. However, if you've not been previously vaccinated, it's recommended that you receive 1 dose of a measles-containing vaccine if you're travelling outside Canada.

It's recommended that you receive 2 doses of a measles-containing vaccine if you're:

  • in the military
  • a health care provider

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Adults born in or after 1970

Most adults born in or after 1970 have received a measles-containing vaccine. In 1996 and 1997, a 2-dose schedule became routine after large outbreaks of measles in Canada. In response, most communities gave a second dose to children and youth who would have only received a single dose.

You should receive a second dose of a measles-containing vaccine if you:

  • were born in or after 1970 and
  • did not receive a second dose of a vaccine

We especially recommend this if you:

  • are in the military
  • are a health care worker
  • are travelling outside of Canada
  • 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 should not have the vaccine

Measles-containing vaccines are generally not recommended for:

  • people who are pregnant
  • infants under 6 months of age
  • people with weakened immune systems

These people rely on others to be vaccinated so that the virus won't spread to them. This strategy is called community immunity or herd immunity.

Safety of measles-containing vaccines

After vaccination, it's common to have mild side effects. They may include swelling, soreness and redness at the site where the vaccine was given. You may also develop:

  • fever
  • stiffness
  • mild rash
  • temporary joint pain
  • face or neck swelling

These side effects usually appear 1 to 3 weeks after vaccination.

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 rash on the skin (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 during a measles outbreak

You're at risk of getting measles if there's an outbreak in your community and you aren't immune. To be immune, you must:

  • be fully vaccinated or
  • have had a lab-confirmed measles infection before

If you're not immune to measles and think you've been exposed, talk to a health care provider. They may recommend the measles vaccine or protective antibodies.

In an outbreak, it may be recommended that you receive the measles vaccine within 3 days of an exposure. This can help prevent measles from developing. During certain circumstances, such as an outbreak, children can receive a measles-containing vaccine as early as 6 months old.

Protective antibodies can help prevent measles from developing. They're only recommended within 6 days of exposure for some people who aren't immune and are at high risk for measles complications. They only provide temporary protection from measles.

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Who is most at risk

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

You're more likely to become infected if you're:

  • unvaccinated or non-immune and
  • travelling to countries where measles is circulating

Occasionally, a returning traveller who becomes infected abroad can spread infection in Canada. This can be a particular problem if the traveller returns to a community where many people are unvaccinated or not fully vaccinated.

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