As you can see the south appears to be particularly hard hit this year which made me wonder how this lines up with states who rejected medicaid expansion under the ACA. My thesis is that if more people are covered by Medicaid you should see an increase in people getting flu vaccines, since they are now essentially free.

Here is a map I found of States that rejected the Medicaid expansion

I think this does line up a bit more than chance would suggest. Sure there are plenty of other reasons that could explain the correlation here, but I think this does merit at least a bit more research.

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**UPDATE:**

A friend of mine did a little more research into this and posted this on my Facebook page

Seemed interesting enough to look into. I pulled 18+ flu-vaccination rate data from the CDC (http://www.cdc.gov/.../rep.../reporti1314/reportii/index.htm) for 2012-2013. I used that year because California and Mississippi were missing data from the last several months of 2013-2014. The 27 states + DC that opted in had an average vaccination rate of 43.8%. The corresponding number for the 23 opt-out states was 41.8%. There is a lot of overlap in the confidence intervals, which isn't surprising given the sample sizes. Running a Mann-Whitney U test results in a U statistic of 248. Approximating with a normal distribution gives a one-sided p-value of 8.1%. So it's not overwhelming but there's some evidence that states that declined the Medicaid expansion had lower rates of flu vaccination.