Just chiming in to add some data I ran across earlier today. The spreadsheet showcases data from Israel which was updated yesterday, 8/3/21. I found it very valuable as it broke down demographics by age and vaccination status.
This clearly shows a significant portion of the new cases are among the vaccinated.
Anecdotally, those I know who have "breakthrough" cases are having fairly moderate flu-like symptoms. I am quite confident those who are symptomatic are capable of spreading illness even if the vaccinated as a population are less likely to transmit disease.
https://docs.google.com/spreadsheets/d/1Mg6NEp4iKcSR1O8l47bL...
The source for the data is linked in spreadsheet. You can copy/paste the link in google translate.
Imgur links of relevant translated data: https://imgur.com/a/uV2wP5B
This clearly shows a significant portion of the new cases are among the vaccinated.
Anecdotally, those I know who have "breakthrough" cases are having fairly moderate flu-like symptoms. I am quite confident those who are symptomatic are capable of spreading illness even if the vaccinated as a population are less likely to transmit disease.