Experts anticipate Pfizer vaccine will be effective beyond six months, but it's still too early to determine that On Thursday, Pfizer announced its vaccine is highly effective at least six months after getting the second dose. Author: Adriana De Alba, Associated Press Published: 7:38 PM EDT April 1, 2021 Updated: 7:38 PM EDT April 1, 2021 VIRGINIA, USA — Just a day after Pfizer and BioNTech announced its COVID-19 vaccine is safe and effective for children as young as 12, the companies announced more promising news Thursday. Citing updated trial data, Pfizer announced its vaccine is 91% effective against COVID-19 for at least six months. The announcement is the first of its kind. So far, Pfizer is the only vaccine manufacturer that has given us an early look at how long the vaccine can provide protection. Pfizer also announced its vaccine is effective against the South African variant, which has been a worry for health officials.