Do I need a measles vaccine dose? What to know

Amina Zafar · CBC News

· Posted: Mar 05, 2025 4:00 AM EST | Last Updated: March 5

Measles is simply a respiratory illness caused by a highly contagious microorganism that's much infectious than influenza, chickenpox oregon COVID-19.

Measles illnesses thin to beryllium mild, but the severity tin scope from ear infections and pneumonia to swelling of the encephalon called encephalitis — which tin pb to convulsions, deafness oregon intelligence disability. In 1 lawsuit successful Ontario successful 2024, measles led to the death of a child nether property five.

"I'm acrophobic successful that the wide vaccination sum is overmuch little successful Canada than is needed to halt measles successful its tracks," said Dr. Theresa Tam, Canada's main nationalist wellness officer.

Measles symptoms include:

• Fever.
• Cough.
• Red, watery eyes.
• Runny nose.
• Koplik spots — small, achromatic spots that hap connected the wrong of the cheeks.
• A rash that usually begins arsenic flat, reddish spots connected the look and spreads to the trunk, arms and legs.

The microorganism that causes measles spreads done the aerial and by interaction with respiratory secretions from the chemoreceptor and mouth.

Droplets containing the measles microorganism tin enactment successful the aerial for respective hours, and the microorganism remains infectious connected contaminated surfaces for up to 2 hours.

Here's what nationalist wellness doctors accidental astir preventing measles.

Why does measles dispersed truthful easily?

Contagiousness sets measles isolated from different infectious diseases.

A azygous idiosyncratic "infected by measles tin infect nine retired of 10 of their unvaccinated adjacent contacts," according to the World Health Organization. "It tin beryllium transmitted by an infected idiosyncratic from 4 days anterior to the onset of the rash to 4 days aft the rash erupts."

There's nary circumstantial attraction for measles. Doctors enactment to alleviate symptoms, forestall complications and support patients comfortable.

Who is astatine hazard of measles?

"All persons who person not had a erstwhile measles corruption oregon who person not had 2 doses of a measles-containing vaccine are astatine hazard of measles infection," according to the Public Health Agency of Canada's website.

When unprotected infants and children bash drawback measles, they look a scope of imaginable wellness impacts.

Among two-year-olds, sum for 1 dose of the measles, mumps and rubella (MMR) vaccine decreased from 89.5 per cent successful 2019 to 82.5 per cent successful 2023, researchers from the Public Health Agency of Canada reported. It besides fell among seven-year-olds.

"Vaccination tin forestall not lone measles infections, but besides the truly important complications that tin originate from measles infection," said Dr. Sarah Wilson, a doc with Public Health Ontario.

The MMR vaccine has been astir for decades.

"The main risk [for infection] is vaccination status," said Dr. Ninh Tran, aesculapian serviceman of wellness for Southwestern Public Health, which includes Oxford County, Elgin County and St. Thomas successful Ontario.

The Canadian Immunization Guide recommends 2 doses for susceptible groups, specified arsenic health-care workers and subject personnel.

A dose is besides suggested for susceptible travellers calved earlier 1970 who are heading to destinations extracurricular of Canada, according to the National Advisory Committee connected Immunization.

Before measles vaccines came connected the scene, astir radical caught the disease. That's wherefore astir adults calved earlier 1970 are presumed to person acquired immunity from past exposure.

WATCH | What makes measles truthful contagious:

Vaccination is specified an effectual instrumentality that measles has been considered eliminated successful Canada since 1998, meaning travel-related cases hap occasionally. If section transmission of measles occurs for a year, Canada risks losing elimination status.

People who person had measles erstwhile can't get it again, wellness officials say.