No such fact exists.
"Vaccination with BNT162b2 reduces transmission of SARS-CoV-2 to household contacts in Israel"
https://www.medrxiv.org/content/10.1101/2021.07.13.21260393v...
> The overall vaccine effectiveness against transmission was 88.5%.
https://www.bloomberg.com/news/articles/2021-07-23/pfizer-sh...
When the virus infects someone that is vaccinated there are less symptoms, less viral load and less risk of further transmission.
And I don't think anyone has done a study on the efficacy of vaccination preventing superspreading, but I suspect that vaccinated individuals are rarely, if ever, superspreaders.
Also that is contradicted by the NEJM study today that finds that Pfizer is still 88% effective against Delta:
https://globalnews.ca/news/8050563/pfizer-astrazeneca-vaccin...