However, using typical establishment spin, Walensky also suggested that the vaccines did prevent transmission of the original variants despite the fact that there was no concrete data to support this notion.

Her explanation for the confusion?  It was "evolution of science" and the virus that changed the conditions, rather than the CDC being wrong (or lying) about the science and the conditions. 

In the video below, Pfizer executive Janine Small is cornered by a member of the European Parliament and openly admits that the company's covid vaccines were never tested for blocking transmission.  This was after Pfizer had consistently claimed the vaccine prevented the spread of the virus.  Media damage control argued that even though the mRNA products were not tested for transmission prevention by Pfizer, they are still considered useful for disrupting spread.  Data so far suggests that this was a lie:

In 2021, data from the Public Health England and the NHS shows that the vaccinated and unvaccinated had almost identical rates of infectiousness. In other words, a vaccinated person was almost as likely to give you covid as an unvaccinated person.

In the case of the original "wild virus" variant from 2020 to 2021, infections and fatality rates actually plummeted well before the vaccines were widely introduced.  This means that natural immunity was the most likely factor in the slowdown of the spread.  Transmission was stopped by the human immune system, not the vaccines.