On August 10, the Oxford University Clinical Research Group published a study  that said those who are fully vaccinated carry 251 times the amount of COVID-19 viruses in their nostrils than those who are unvaccinated.
The study posits that those who are vaccinated carries “unusually high viral loads” while not becoming ill because the vaccine is moderating symptoms. This possibly turns the vaccinated into “presymptomatic superspreaders.”
The 31-page study findings  included a failure of the AstraZeneca and Johnson & Johnson vaccine to limit the spread of the virus in a controlled, two-week hospital lockdown in Ho Chi Minh City, Viet Nam.
Sequencing of strains conducted on healthcare workers after the lockdown showed that vaccinated workers “acquired, carried and presumably transmitted the Delta variant to their vaccinated colleagues.” For the purpose of this study, “fully vaccinated” refers to approximately two months post-vaccine.
Farinholt and colleagues  in the US made observations with similar findings.
The Centers for Disease Control and Prevention also said in early August  to say that the COVID-19 vaccines are not effective against the transmission of SARS-CoV-2. CDC Director Dr. Rochelle Walensky told CNN, “Our vaccines are working exceptionally well. They continue to work well for Delta, with regard to severe illness and death — they prevent it. But what they can’t do anymore is prevent transmission.”
Hence, the mask recommendations (or requirements) are back regardless of vaccination status.