Vaccines are a side show to the autism discussion, I know. And, yes, I know I spend a lot of time on this side show. One reason is that the autism parent community has a segment which does a lot to harm public health by creating fear of vaccines. With the resurgence of measles in the U.S., we are seeing the discussion rise again. For example, Dr. Robert “Bob” Sears has chimed in on facebook (see a discussion at Respectful Insolence here) as has Dr. Jay Gordon on twitter (see a discussion at The Poxes).
Inevitably these discussions include statements about how people suffer injuries or even death from measles. This is then countered by claims that with good nutrition, sanitation and vitamin A, no one will suffer lasting consequences. The CDC makes this very clear:
Even in previously healthy children, measles can be a serious illness requiring hospitalization. As many as 1 out of every 20 children with measles gets pneumonia, and about 1 child in every 1,000 who get measles will develop encephalitis. (This is an inflammation of the brain that can lead to convulsions, and can leave the child deaf or mentally retarded.) For every 1,000 children who get measles, 1 or 2 will die from it. Measles also can make a pregnant woman have a miscarriage, give birth prematurely, or have a low-birth-weight baby.
But people think this is an acceptable risk, or downplay this risk. One way they do this is to estimate risk of harm by the fraction of the total population, not the fraction of the population infected. That made some sense in the old days when a sizable fraction of the population was infected each year and everyone would be infected at some point in their lives.
Consider this old graph. In a bit we will get to the edit that was done and how deceptive that is (click figure to enlarge):
The rate of measles infection dropped by about 30x between 1964 (before the introduction of the vaccine) and 1971. With that came a drop in deaths from measles. A factor that is very interesting, and very much misused, is the fact that the death rate from measles was steadily dropping before the introduction of the vaccine. Hence the “vaccines didn’t save us” myth. Had we just waited, the death rate would have dropped to the same level anyway. There’s a line extrapolating from the data that “shows” that.
First off–hooray for medical advances. They have improved the survival rate from measles. Damned glad they did. But, what about that line? Well, you can draw a line through pretty much anything if you try hard enough. It doesn’t mean anything if you don’t understand the mechanism causing the trend. Why should we expect the trend before 1965 to continue for the next 45 years?
While engaging in online discussions about measles outbreaks, I ran across this website from the U.K.. The table is “Measles notifications and deaths in England and Wales, 1940-2013”. The public health officials in the UK are supposed to be “notified” of every person infected with measles, so “notifications” are “cases”. Let’s consider the notifications. (click figure to enlarge)
This isn’t normalized to the total population, it’s just the raw number of cases in any given year. I’ve taken the liberty to point out some events which happen to coincide with changepoints in the graph. First is the introduction of the measles vaccine, after which the number of cases per year dropped dramatically. Second is the introduction of the MMR vaccine which, again, was followed by drops in the number of cases. Lastly we see the publication of Andrew Wakefield’s now-retracted Lancet study. Shortly after which, the number of cases started to rise again. Yes, correlation is not causation, but time after time, with vaccine after vaccine we see the same thing: introduce a vaccine and the incidence of that disease decreases.
OK, we’ve looked at notifications. What about deaths? Let’s take the number of deaths and normalize by the number of notifications. In other words, let’s look at what fraction of those infected died.
Pre 1960 there was a steady drop in the fraction who died. Again, yay medicine. And, yes, yay nutrition and sanitation. After 1960, though, the fraction who died leveled off. 2-3 people per 1000 infected died. (it averages to about 2.6/1000 from 1960 onward).
None of this is news. In Measles Elimination in the United States, a team from the CDC writes:
By the late 1950s, even before the introduction of measles vaccine, measles-related deaths and case fatality rates in the United States had decreased markedly, presumably as a result of improvement in health care and nutrition. From 1956 to 1960, an average of 450 measles-related deaths were reported each year (∼1 death/ 1000 reported cases), compared with an average of 5300 measles-related deaths during 1912–1916 (26 deaths/ 1000 reported cases)
Catch that–that’s people from the CDC saying “yay healthcare! Yay nutrition!” and “yay vaccines!”.
Did nutrition, sanitation and improved medical care reduce the fraction of people who died from measles infection? Absolutely. Was it enough? No. Can we draw lines from old data and claim that the number who would die today would be 4 in 100 million today? Well, sure, you can draw the line. It’s dishonest, but given the source that’s not surprising. As I wrote above, you can draw a line through anything. Doesn’t make it true. If you don’t know the reason why a trend is happening, or the limitations on that trend, it’s meaningless. In this case there was a “hard floor”. There are deaths from measles that sanitation, nutrition and modern medicine can’t prevent. People still die from measles. Measles deaths in France (modern sanitation, nutrition and medicine) were seen at a rate of 3/1000 in recent years. Pregnant women, fetuses, small children and the infirm are more likely to suffer. Which is why when people like “Dr. Bob” Sears and “Dr. Jay” Gordon downplay the risks of measles–in effect telling their readers to keep relying on the rest of us to provide herd immunity–people like me speak up. Yes it’s a diversion from autism, but it’s a diversion fed by some of my fellow autism parents. And it’s an important diversion.
By Matt Carey