A fully vaccinated person can have a breakthrough infection and transmit the virus, but low probability.
Though COVID-19 vaccines are effective against virus variants, including Delta, there is a chance of fully vaccinated people getting infected. There is also a possibility of spreading the virus to others. At the same time, it is important to note that COVID-19 vaccines offer good protection from severe disease and deaths. The infection tends to be mild, and there's less density of the virus in a fully vaccinated person, which means less risk that the virus will be transmitted to somebody else.
The COVID-19 pandemic has given rise to a lot of potentially dangerous misinformation. For reliable advice on COVID-19, including symptoms, prevention, and available treatment, please refer to the World Health Organization or your national healthcare authority.