Skeptics Café

Originally posted here; this article shows how convincing-looking graphs can be misused. Robert Webb writes:
The anti-vaccine movement sometimes presents graphs to support their cause, supposedly to show that diseases were on the decline before vaccines came along, and that vaccines had no effect. Graphs seem hard to argue with. They look scientific, represent actual data, and are compelling to many people. And indeed a good graph should be compelling. But their graphs are not good. Let’s have a look at how the true data, which supports the fact that vaccines have had a huge positive effect, can be manipulated to manufacture the conclusion the anti-vax movement wants.

Death rates

Firstly, most of the graphs they show are of death rates, not infection rates. Yes, death rates dropped significantly before vaccines were introduced because other improvements in medicine and sanitation meant that we were better at treating the disease, but it does not indicate that less people had the disease to begin with.
They also tend to show graphs going back a long time to when death rates for common diseases like measles were very high. To fit these high figures on the graph it’s necessary to scale down all the figures, meaning that by the time the vaccine is introduced you can no longer see any drop it may have caused in deaths.
They never show graphs of death rates from third world countries where due to poor sanitation etc. death rates for diseases like measles can still be quite high.
Here’s a nice graph though showing both infection and death rates in the US and it’s clear from both that the 1963 vaccine had a huge effect.

The anti-vaxxers claim (e.g. here) that death rates are more reliable than infection rates because they don’t trust the diagnoses made by doctors. The idea is that doctors are biased against View More Analysis of Anti-Vax Graphs