In my own understanding, a currency of given country’s strength depends upon her productivity. And not only productivity. Are her products and services essential needs and wants to a large demands, thus, drives productivity.
I argue so having US dollar in my view and why it’s a yard stick of the most world currencies. Let me base my point with 1700-1914, an age of revolution. At the time, let me pick just two inventions: Anesthesia; a product invented by an American, William Morton, that gives sugary services world wide. Airplane invention, by two Americans, Orville and Wilbur Wright.
Now, in simple terms, world over purchases theses products, hence, enriching dollar.
Reversing back to Covid-19 vaccines. America has three among top five; Moderna, Pfizer/BionNtech and Johnson & Johnson Janssen which African Union has selected and started dispatching to its members, with fill-finish activities taking place in South Africa, and in the process enriching US dollar with African currencies hence giving China’s renminbi a beating.