This is what happens when we don't vaccinate

The Centers for Disease Control released a report this week on the measles outbreaks that have happened in the United States since the beginning of 2011. The report covers 19 weeks, and 118 cases of measles, which group into clusters that speckle a map of the U.S. like, well, like a case of the measles.

Let's remember, getting the measles is not like catching a cold. There are serious risks of serious complications. Seth Mnookin—whose book, The Panic Virus, is something you really should read—says measles has killed more children than any other disease in recorded history. In a post at his blog, Mnookin looks at the CDC report, and what we can learn from it.

* There have been 118 reported measles cases in the first nineteen weeks of the year—which is the highest number of infections for that period since 1996. That's particularly noteworthy because, as the CDC points out, "as a result of high vaccination coverage, measles elimination (i.e., the absence of endemic transmission) was achieved in the United States in the late 1990s and likely in the rest of the Americas since the early 2000s."

Endemic transmission refers to long strings of measles outbreaks, without a distinct beginning or end. If you have a population with high vaccination rates, you can effectively wall off a rare case or two of the disease. Someone picks it up (often because of a trip overseas) and spreads it to a few other vulnerable people, but the chain of transmission ends within a few weeks or months. In endemic transmission, the chain just keeps going, for years. Without vaccine "walls," you don't have outbreaks during which you must be careful, you have a constant threat that never goes away. This is, essentially, what has already happened in France.

* Eighty-nine percent of all reported cases have been in people who've been unvaccinated. Almost 20 percent of that figure is made up of children who were less than a year old. That means they were too young to have received the first dose of the measles-mumps-rubella (MMR) vaccine, which is given once between the ages of twelve and fifteen months and again when a child is between four and six years old. Another twenty percent of the total number of reported infections were in children between the ages of one and four.

In other words, choosing to not vaccinate some children affects the health of other children whose families haven't made that choice.

* Forty percent of the infections recorded so far this year have resulted in hospitalization—and 98 percent of the people who were hospitalized were unvaccinated. In its typically understated manner, the CDC noted that "nine [of the hospitalized patients] had pneumonia, but none had encephalitis and none died"—which is another way of saying that encephalitis and death are potential complications of serious cases of pneumonia.

And all of that is expensive. Containing a single outbreak—caused by an intentionally unvaccinated patient—with just 12 cases, cost us $150,000. That's not much money in the grand scheme of public health, but it is money that we shouldn't have had to spend. And endemic transmission, at the scale of what is happening in France, would be a lot more costly. There've been 6400 measles infection cases in France this year, Mnookin says. In the U.S., with our larger population, an outbreak of that size would have meant 28,000 cases here. With a transmission rate of 90%, measles cases, and the costs to contain them, can stack up very quickly.

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