The intellectual system that maintains knowledge of things like vaccination does not exist simply in books;  it requires a great deal of support.  Cheap energy underwrites that support.  

For each realm of knowledge or each technology, you can ask what must be maintained in order for it to function.    Practical things:  Glass making, wire making, an educational system that trains people in these things and teaches the public at large what they are about.  

Do not underestimate the role of corruption in poisoning the function of large institutions that we have been depending on and counting on to maintain these things.  When pharmaceutical companies are happy selling poisons as effective drugs, the whole concept of modern pharmacology is put at risk.  The malignancy of genetic engineering has long term implications for molecular biology.  

I don't mean (nor think) that everything will go.  But a lot will.  High maintenance knowledge is an endangered species.  

The Fates are kind.