What am I missing here?

https://en.wikipedia.org/wiki/Jonas_Salk

We got the needles when we were young.

They had one for measles also.

https://www.cdc.gov/measles/about/history.html

I believe we got both as children of Jack & Mary.

https://www.nytimes.com/2010/08/05/health/05peebles.html

And Dr Peebles got a 'D' in Biology!

So what am I missing here about a measel epidemic?

https://www.doctorswithoutborders.org/what-we-do/medical-issues/measles?source=ADD190U0U05&utm_source=Bing&utm_medium=PPC&utm_campaign=BingAds&utm_content=NonBrand&msclkid=32e4342c75f0148a993768e65b753c72

Why is that happening?