https://www.siliconvalley.com/2021/07/28/pfizer-data-suggest-third-dose-of-covid-19-vaccine-strongly-boosts-protection-against-delta-variant/

A third dose of the Pfizer/BioNTech Covid-19 vaccine can “strongly” boost protection against the Delta variant — beyond the protection afforded by the standard two doses, suggests new data released by Pfizer on Wednesday.

The data posted online, which are expected to be discussed in a company earnings call on Wednesday morning, suggest that antibody levels against the Delta variant in people ages 18 to 55 who receive a third dose of vaccine are greater than five-fold than following a second dose.