It's important to understand that what CDC & FDA etc say is not "science".

These are federal regulatory agencies whose mission is to enforce regulations. This is part of a political process, and their leaders ultimately serve at the pleasure of the president.

When the prominent scientists who work there speak on issues, they are speaking as employees of that organization, not giving their best scientific estimation.

The WHO is a UN agency that's probably even more politicized, but I don't know much about it.