It is my understanding that the problems this administration has with the coordinated effort included:
1. The USA would be covering a disproportionate cost towards the development and distribution of the vaccine
2. The USA would be agreeing that a disproportionate amount of the first doses of the vaccine would be going to other countries around the world; rather than, our own US population.
3. This administration does not trust the WHO in managing or overseeing this process as a whole.
With the USA having 3 viable vaccine options in or entering phase 3 trials, it appears this administration is content betting our our country's ability to develop, manufacture, and distribute a vaccine in our country. Then, focus more on helping the rest of the world.