We're one of the nation's least-vaccinated areas. Now we've got a measles outbreak in Clark County. Are we the first to suffer real-world consequences from not vaccinating our kids? —Typhoid Harry

Not even close. The worst U.S. measles outbreak of the post-vaccination era was in eastern Ohio in 2014, with 383 cases reported. (In fairness, the non-vaccinating parents in that case had a better excuse than ours do—they were Amish.)

The worst case that can be blamed directly on Jenny McCarthy was over the winter of 2014-15, when some unknown genius took his measles to Disneyland. Eventually 125 mostly unvaccinated cases would be traced back to the park, leading the California legislature to strengthen its mandatory-vaccination rules.

By these lights, the 21 cases recorded in Clark County are barely a blip. But don't give up hope! This outbreak isn't over yet, and with some Portland preschools reporting vaccination rates as low as 40 percent—the equivalent of a forest whose brush hasn't been cleared in 60 years heading into wildfire season—we're just one well-placed sneeze away from making history!

Luckily (sort of?), there is one fact that tends to go underreported in stories like these: As diseases go, measles isn't all that deadly. In the last five years before the introduction of the measles vaccine—that's 1958 to 1962, for those who are counting—just under 1 case per 1,000 reported resulted in death.

That's not nothing—you'd get a similar mortality rate from letting a crazed gunman empty a clip at a Timbers game, and we* consider that a worthwhile thing to try to prevent—but ebola it ain't.

Thus, we can posit a sort of Darwinist, crunch-all-you-want-we'll-make-more argument for allowing childhood diseases to run their course and cull the herd. It's pretty much the same argument that says small-claims court should allow flamethrowers, but it's there.

Yet I must say I'm surprised at how many gluten-free, anti-vaxxer moms—to outward appearances so overprotective—seem, deep down, to share my unorthodox opinions regarding acceptable casualty rates for the 5-and-under crowd. Are they really so willing to throw those 999-to-1 dice with their kids? Or do they just suck at math?

* Some of us, anyway.