Getting vaccinated against common infectious diseases is just good common sense, for the vast majority of people.

But plenty of people dissent from that view. For various reasons (mostly not based on science) they decide not to get their kids vaccinated.

The decision not to get vaccinated is often seen as a personal choice, as a matter of individual choice.

It鈥檚 not.

Firstly, it鈥檚 almost always a choice being made on behalf of children too young to make up their own minds.

Chicken pox, the measles, rubella 鈥� these used to be considered 鈥渃hildhood diseases鈥� because it was almost impossible to get through childhood without contracting them.

Now a whole generation has missed out on that experience, but feels like it鈥檚 fine to make the decision to be exposed to a misery-inducing, occasionally fatal disease for their offspring.

Second, and just as important, is the concept of herd immunity.

Remember how getting vaccinated is common sense for the vast majority?

There are a tiny number of people who can鈥檛 get vaccinated, because of serious allergies or immune disorders. They remain vulnerable to infectious diseases, and rely on the rest of us getting our shots to protect them. They can鈥檛 get chicken pox or the mumps if it isn鈥檛 circulating in the community.

That goes double for the measles, which is amazingly infectious.

Finally, we鈥檙e seeing an interesting trend as the measles outbreak spreads from the U.S. up into Canada.

Teenagers whose parents chose not to get them vaccinated are sneaking out to get their shots. It turns out that while their parents may have opted out, the kids for whom the decision was made are starting to have their own ideas about what鈥檚 best for them, and for their communities.