Canada Is Losing The War On Measles

As Canada losing their elimination status for measles is a nerve-wracking reminder of the fragility of modern civilization

In 1998, following an intensive multi-year vaccination campaign that brought the nationwide measles vaccination rate above 95%, Canada officially eliminated measles. On November 10th, Canada lost that elimination status. Measles is officially endemic in Canada for the first time in.

We are going to talk about how this happened, what this means (for both Canada and the United States), what the dangers are, and what can be done about it.

Define Elimination

The first thing we need to do is come to an understanding of terms. During the Covid pandemic, I became fascinated with the history of disease eradication (which is not a synonym for elimination) because so many of the strategies for Covid containment drew from this theory that Covid could be contained with the same strategies we used to contain smallpox and polio.

In this discovery mode, I learned that there is a big difference between “elimination” and “eradication” which is incredibly annoying because they seem to be describing similar things and they both start with “e”.

In the context of disease management, “eradication” means that there are zero detected cases of the disease in a given region for a period of 3 consecutive years. When the WHO was attempting to eradicate smallpox in the 1960’s and 1970’s, they insisted that any region requesting the eradication status allow their researchers to conduct disease surveillance. Eradication is a big deal and the only disease that has been successfully eradicated is smallpox (though polio is close).

The “elimination” of a disease is a much lower hurdle. Simply put, elimination means that the disease is not spreading naturally within a given country or region. As with measles, the disease may be introduced through some foreign source, but the outbreaks are usually small and ultimately contained. A few people might get sick, but it doesn’t spread from town to town.

The formal public health definition of elimination is that the disease spread does not last for more than 12 months. This 12 month mark is important because disease spread is incredibly seasonal, driven by population-level changes in human behavior that are impossible to control. There might be an outbreak that was started by a foreign introduction and went around a town or city for a few days or weeks and then died out. The important thing is it died out. It will require another foreign introduction to get more people sick.

But if people are contracting new cases of the disease from local sources over the course of a full year, that means the disease is endemic and is managing to survive and infect people through an entire seasonal infection cycle. This means that foreign introductions are not required for the disease to spread and can potentially continue infecting within that population indefinitely.

That’s bad.

Oh, Canada

Back to Canada. The reason Canada lost its elimination status is because exactly this thing happened. Measles has been spreading within communities in Canada for over 12 months. It has become endemic, which means that is is consistently present.

How did this happen? There are many theories but it seems like the most coherent one is connected to the Canadian Mennonite community. The Mennonites are a Christian religious sect (denomination? I’m not sure) that has fairly low rates of vaccination. The ongoing spread in Canada seems to have originated from a Mennonite gathering in Ontario about a year ago and has spread continuously in nearly every province since then.

It’s difficult to know exactly what is happening with the data I’ve been able to obtain. Canada has had over 5,000 cases of measles in the last year but they only have 150,000 Mennonites. If these cases were even a majority of measles cases, that puts the rate of infection in the Mennonite community at about 2%. This is really high but it’s also pretty much in line with the rate of measles infection in the famous Samoan measles outbreak of 2019.

Canada seems to be in this pattern where there is a serious and large measles outbreak in a tight-knit community with very low vaccination rates, which then leak into the larger population and cause flare-ups, which die out because of the higher vaccination rates.

Elimination Round 2

There has been a lot of talk about measles in the United States (because it’s been a bad year for measles), but it really has been much worse in Canada. Keep in mind that Canada’s population is only 12% of the US population. If we charted Canada’s measles rate against the US, the US would look like a flat line.