As new coronavirus variants test the protections of the available vaccines, federal health officials say there's no need for booster doses right now.

"Americans who have been fully vaccinated do not need a booster shot at this time," read a joint statement sent Thursday from the Centers for Disease Control and Prevention and the Food and Drug Administration.

The agencies added that people who are fully vaccinated are protected from severe illness and death, including from emerging variants such as the highly contagious delta variant that's now the dominant strain in the U.S. and in other countries.

The news comes shortly after Pfizer and BioNTech announced plans to seek FDA authorization for a booster dose of their COVID-19 vaccine.

Pfizer and BioNTech say initial trial results from an ongoing booster trial show that a third shot given six months after the initial two shots can bring antibody levels to a point that should increase protection against disease caused by either the original strain of the coronavirus or the beta variant (the variant first detected in South Africa).

Pfizer and BioNTech say they are also developing a new version of their vaccine designed specifically to target the delta variant, which they hope to start testing in volunteers this summer.

NPR's Joe Palca contributed to this report.

Copyright 2021 NPR. To see more, visit https://www.npr.org.