Vaccination, immunity and records: Your questions on measles, answered

Canada continues to see an alarming rise in measles cases in 2025.

Through the spring, the virus spread most intensely in Ontario. But after over 2,200 cases, hundreds hospitalized and one measles-related death, it seems to be dwindling in that province.

Now, Alberta's seeing a spike, with almost 1,300 confirmed cases so far.

With every province except Newfoundland and Labrador reporting cases of measles, here are some common questions from CBC readers, viewers and listeners — answered.

Most likely yes, says the Public Health Agency of Canada (PHAC).

It says those who have had a past measles infection should be immune against another one, as long as they have a normal immune response.

Generally, yes, says PHAC.

PHAC recommends that children and adults who don't have records of their vaccination history be started on an immunization schedule appropriate to their age and risk factors.

Even if you've already been vaccinated, it's generally considered safe for health-care providers to give another dose, PHAC says, because they haven't seen additional side effects from repeated immunization.

But this is why a national vaccine registry would be hugely helpful, says Dawn Bowdish, a professor of immunology at McMaster University.

"The number of people who are looking to figure out if they got one dose, if they got two doses, if they were vaccinated as children and perhaps they just moved provinces and they can't get their records is extremely high."

Two doses of the measles, mumps and rubella vaccine offer almost 100 per cent effectiveness against the virus in the long term.

That depends.

PHAC says routine testing for laboratory evidence of measles immunity is not recommended for the general population.

Some populations, like health-care workers who work with vulnerable people, as well as some pregnant women, can get a blood test looking for antibodies against measles.

Those who have received two doses of a measles-containing vaccine, or those who are born before 1970, are presumed to be immune against the virus.

No. Proof of vaccination is not mandatory to enter Canada.

Canada does require permanent residents and certain temporary residents to have an immigration medical exam before arriving in Canada, said a spokesperson for Immigration, Refugees and Citizenship Canada. The test also screens for certain communicable diseases.

During that medical exam, some may be offered vaccinations — including the measles, mumps and rubella shots.

Doctors who work with recent immigrants and asylum seekers tell CBC News their patients generally don't hesitate to get any childhood vaccinations they might have missed.

But, they say, the federal government can do more to ramp up pre-departure vaccination programs, and make it easier for health-care providers to access medical and vaccination records across borders.