From immunologist and virologist Robert W Malone, MD:
Delta has an Ro of about 8, about 3x that of the Alpha (ref- CDC). With these leaky vaccines, if we were to have 100% vaccine uptake and perfect mask use we cannot stop the spread of Delta (ref- CDC).
the current vaccines provide about 50-60% efficacy in protection from infection. They are not fully protective.
if you are vaccinated and become infected (“breakthrough”), the virus will replicate at the same or higher levels than if you were unvaccinated and then become infected.
if you are vaccinated and then become infected, your risk of transmitting virus to someone else is quite high – remember, the Ro measures how likely you are to transmit the virus.
if you are vaccinated and then become infected, your risk of developing severe disease or dying is better than if you were not vaccinated and then become infected with Delta.
Therefore, if you are vaccinated and then become infected, you MAY have a higher risk of becoming a “superspreader” because you are less likely to show disease. This has not been measured, but it should be.
You can read more from Dr. Malone here.