All 50 U.S. states were notified by the Centers for Disease Control and Prevention to be ready for the massive distribution of a COVID-9 vaccine by Nov. 1, a document obtained by news outlets on Wednesday showed.

In the letter dated August 27, CDC chief Dr. Robert Redfield disclosed the center had collaborated with biotech group McKesson Corp for the planned distribution of hundreds of millions of doses to hospitals and medical centers across the U.S.

Redfield termed the effort as "large-scale" and requested the assistance of state governors in accelerating the application process for the set-up of distribution centers that will be manned by teams from the McKesson group.

The CDC also sent planning documents to selected medical departments that included potential timeframes for the distribution of the vaccines.

The letter also disclosed that initially available treatments will either get emergency authority use by the Food and Drug Administration or by the CDC under its emergency powers.

The timing of the announcement has sparked some doubts over the likely politicization of the vaccines' distribution, which the Trump administration has repeatedly mentioned it expected to be carried out before the November 3 U.S. general polls.

A planning paper that the New York Times obtained outlined the vaccine situation as "uncertain and evolving" but it drew a speculative supply and operations layout for doctors and local health authorities.

One framework indicated two million vaccines being rolled out by end of October, and another suggested 10 million to 20 million doses being available by the end of November.

According to Redfield, officials were preparing for what he expects would be a "reality" that one or more vaccines will become available in November or December.

The likelihood that a COVID-19 drug will be available by then has been heavily disputed by top health officials, including former FDA director Dr. Scott Gottlieb.

Full approval of the vaccine for the U.S. population, Gottlieb said, when everyone else can head out to consumer value stores and buy a shot, is "really a 2021 event."