A booster dose of the COVID-19 vaccine developed by Pfizer Inc and German partner BioNTech SE was 95.6% effective against the coronavirus when compared to a vaccinated group that did not get the third shot, data from a large study released by the companies showed on Thursday.

The companies in a release said the booster was tested on 10,000 participants aged 16 and older who had received two doses in its earlier trials. A booster administered about 11 months after the second shot had a favourable safety profile and worked against the highly contagious Delta variant of the coronavirus, they said. The data has not been submitted for peer review.

The trial results come a day after the U.S. Food and Drug Administration authorized booster doses U.S. FDA clears Moderna, J&J COVID-19 boosters, backs use of different vaccine for boost of the COVID-19 vaccines from Moderna Inc and Johnson & Johnson, and said Americans could choose a different shot from their original inoculation as a booster.

An panel of expert advisers to the U.S. Centers for Disease Control and Prevention made a similar recommendation on Thursday, clearing the way for a final approval from its director that would allow such shots in the coming days.