All 50 states don't have to agree, only states and their immediate neighbors, Europe (for example) was able to interconnect itself with highways without a unitary government and the nation states on that continent are FAR more diverse and have deeper division than our states do. The only thing you get with the federal government running things is wasted resources and inefficiencies.
Why do we need "national vaccines"?????? apparently you're unaware that consumers are the drivers of the quality, effectiveness and cost of what they consume NOT government, "national standards" only serve to inhibit innovation and cost reduction while facilitating graft and reduced competition.
Is that a white flag I see before me? why yes I believe it is.
"
When the debate is lost, slander becomes the tool of the loser." -
Socrates
Without the states there is no Republic, the trend has been to transform the Republic into a unitary nation state which is NOT The United States and what you're arguing for is a continuation (and acceleration) of that trend. I don't need people on the opposite side of the country to have a say in that conduct of my day to day affairs and I doubt those people want me having a say in theirs. The States are perfectly capable and uniquely situated to take care of the vast majority of the governmental needs of their citizens without involvement from the remote, self-serving, corruption soaked and inept organism that lives in Washington D.C..