Third Pfizer Vaccine Dose Ratchets Up Protection Against Delta Variant

Pfizer announced that a third dose of its COVID-19 vaccine offers much stronger protection against the Delta variant than a two-dose regimen. 

A third shot generated an 11-fold increase in protective antibodies in 65 to 85-year-olds and a 5-fold increase in 18 to 55-year-olds than the currently authorized regimen, the company said, citing nonpeer-reviewed data.

The drugmaker projected that a third dose could yield a 100-fold increase in neutralization of the Delta variant when compared against the two-dose regimen.