Originally Posted by Turquesa
The problem with looking at overall rates it that vaccine exemptions tend to cluster in certain communities. If the exemptions were evenly spread throughout the US, the numbers wouldn't be a huge problem.
See this link on the states with the best and worst coverage. Colorado, for example, is at 85% for MMR in kindergarteners. While the "best" states are at 98-99 percent, bringing the overall average up.
They conclude on that link : "High vaccination coverage levels at the national and state levels might mask clustering of unvaccinated children at local levels where vaccine-preventable diseases might be transmitted," CDC researchers wrote, adding that health departments and schools can use the data "to identify schools with low vaccination coverage and high exemption levels"
Basically, a nationwide statistic like that doesn't mean as much in terms of outbreaks. Outbreaks tend to occur where there are pockets of people who do not vaccinate. The nationwide stat is I believe around 92% for the MMR. But there are large pockets and areas in the US where the rate is well below the threshold needed for herd immunity, which is 95% for MMR if I remember correctly.
If 90% of the country vaccinated, and the 10% that don't were widely and evenly spread across the country, it is less likely that a disease with a single entry point will hit many people. But if 92% of the country vaccinated, with some areas reaching 99% and others reaching 85%, the areas with only an 85% rate are extremely vulnerable to outbreaks, both as compared to the areas with 99% and even the areas with 92%.
An immunocompromised person or baby in a community with only a 60% MMR vaccine uptake isn't going to care what the national rate is if someone carrying the measles virus comes through.