The Delta variant does need further research regarding the transmission.
Two studies
1,
2 from Israel, posted as preprints on 16 July, find that two doses of the vaccine made by pharmaceutical company Pfizer, based in New York City, and biotechnology company BioNTech, based in Mainz, Germany, are 81% effective at preventing SARS-CoV-2 infections. And vaccinated people who do get infected are up to 78% less likely to spread the virus to household members than are unvaccinated people. Overall, this adds up to very high protection against transmission, say researchers.
And the highly transmissible
Delta variant is a major source of uncertainty. The Israeli studies and others are based on the circulation of earlier variants, in particular Alpha, but research suggests that vaccines offer slightly reduced protection against Delta.