On August 2, 2021 at a White House Press Briefing CDC Director Rochelle Walensky confirmed that the prevention of virus transmission was not studied in the COVID-19 vaccine clinical trials.
She stated they worked for Alpha variant, but does not with the Delta variant. As such the vaccinated could get infected and “potentially transmit” the virus to an unvaccinated person, she neglects to mention transmission could also occur to another vaccinated person!