In the previous strain vaccines helped lower infection rates but only to a small degree. In the Delta variant, which is quickly becoming the dominant strain, vaccines have almost no effect on infection rates. Keep in mind that the purpose of the vaccine is to help you fight the virus, not to stop you from ever getting it, and it certainly isn’t designed to stop you from spreading covid.
“The new study found that virus levels in a fully vaccinated person who has contracted the Delta variant are similar to those of a person who has not had a vaccination.
https://www.medicalnewstoday.com/articles/delta-infection-unvaccinated-and-vaccinated-people-have-similar-levels-of-virus#Delta
“The CDC revealed that 74% of cases in Barnstable county, Massachusetts were found in people who were fully vaccinated. And they say now that the vaccinated are just as likely to spread the virus as those who are not vaccinated.”
https://youtu.be/KAZTVUwQZaE