The people who were vaccinated had waning immunity because they had been vaccinated in the previous Winter and Spring. People who were infected with Delta were less likely to be re-infected since Delta became dominant strain in July.

The problem now is that Omicron is 16 times more likely to evade antibody response than Delta.

The CDC study you're referencing was conducted before boosters became the recommended course of action after the large Israeli study on waning immunity.

The knowledge about the disease is always being updated. The skeptics like to pull out old information without context.
[Post edited by lchoro at 01/20/2022 12:29PM]