The videos above show the difference in spread of measles in a community – in this case New York – with 80% of school-aged children vaccinated compared with the scenario if 95% are vaccinated.
The simulation was prepared by the Framework for Reconstructing Epidemiological Dynamics, or FRED, at the University of Pittsburgh.
The outbreak in the first simulation is so devastating because the city has lost its herd immunity, which occurs when too few people are vaccinated to protect the community. On the second map a few measles cases pop up, but the population stays protected because enough people are vaccinated.
But as Scientific American points out, the scenario is far from fanciful.
Unfortunately, the average vaccination coverage for one-year-olds across the U.S. was 91 percent in 2013. In 10 states–Arkansas, Colorado, Idaho, Iowa, Kansas, Maine, North Dakota, Pennsylvania, Vermont and Washington–coverage for children in kindergarten was below 92 percent during the 2013-14 school year, according to the U.S. Centers for Disease Control and Prevention.
You can run simulations for other regions here.