Polio makes comeback in Venezuela after decades
medicalxpress.com
medicalxpress.com
Not to mention that they need to learn, eventually they'll need it.
Secondly, Bill Gates was vaccinating only in countries where polio is endemic. His whole thing is once it's gone, it shouldn't come back.
The latest UN HDI data is from 2016 - things have gone /drastically/ downhill for Venezuela since then, especially in the last 6 months.