Vaccination rates in immigrant populations is lower than native born children, but not significantly. As you noted in your link, they're generally willing to get vaccines, but many didn't have access before they immigrated.
Also, the current outbreak was incubated in Mennonite communities before spreading wider. Despite living in Canada for over 100 years Mennonites are still considered immigrants by many because they are insular and different.
In other words, it's a racist talking point that has enough truth to make it non-trivial to challenge, but has no actual basis.
Canada has a mandatory immigrant medical exam for anybody applying for permanent residence or a visa of longer than 6 months. At this exam, the doctor will ask for vaccination records and prescribe missing vaccinations. It is unlikely that immigrants are contributing to this outbreak.
The Mennonites in Canada aren't actual immigrants and are not subject to this mandatory exam.
Where in the article it suggested the spread due to immigration?
If any, it is due to misinformation and reluctance of those communities (mentioned specifically Alberta rural, y’know, the province that has been burned with misinformation, public health scandal, crazy Premier that has been stoking Separatism while cozying with MAGA that has threatened Canada sovereignty)
Measles is unbelievably infectious. An unvaccinated person has a 90% chance of getting infected if exposed. The virus can survive in the air for hours. In a susceptible population, one infected person will typically infect a dozen other people or more.
Changing the rate of immigration won't make a bit of difference for a disease like this. It only takes one infection in a susceptible population, and then it's game over. Unless your controls are 100% effective (including tourists and returning citizens), the only way to prevent an outbreak is for the vast majority of your people to be uninfectable.
An insufficiently vaccinated population is like a can of food. It might take longer to spoil if there's a pinhole in the side versus if you just crack it open, but it will spoil if there's any breach whatsoever.
So unless you propose to isolate to a degree more extreme than North Korea, blaming immigrants is just bigotry.
We all know by now that immigration is going to be cited, by certain people, as the cause of any problem. It's not worth your time to draw out the charade that it's intended to start a good faith discussion. It's better for the platform to downvote and ignore.
