The U.S. Centers for Disease Control and Prevention (CDC) late Thursday approved booster doses of Moderna's (MRNA  ) and Johnson & Johnson's (JNJ  ) COVID-19 vaccines, adding that Americans can mix and match any of the three shots authorized for use in the United States, the agency said in statement.

Earlier on Thursday, the agency's Advisory Committee on Immunization Practices unanimously recommended a third dose of the Moderna shot for the elderly and other more vulnerable adults six months after their initial two-dose regimen, similar to the CDC's ruling on Pfizer (PFE  )-BioNTech (BNTX  ) boosters. The independent panel also backed J&J boosters for all adults who received one dose at least two months ago. The ruling followed the U.S. Food and Drug Administration's independent advisory committee and agency's decision supporting both booster shots.

Following the panel's decision, CDC Director Dr. Rochelle Walensky officially authorized additional doses of both vaccines, making them immediately available for many Americans.

"The evidence shows that all three COVID-19 vaccines authorized in the United States are safe--as demonstrated by the over 400 million vaccine doses already given," Walensky said in a statement Thursday. "And, they are all highly effective in reducing the risk of severe disease, hospitalization, and death, even in the midst of the widely circulating Delta variant."

The CDC's decision to allow Americans, with the advice of their healthcare provider, to mix and match COVID vaccines comes as a recent U.S. National Institutes of Health study that suggested that recipients of J&J's COVID-19 vaccine are better off getting a booster shot of either the Pfizer-BioNTech or Moderna shots.

Booster shots have been a controversy topic for global scientists, with the World Health Organization vocally disagreeing with wealthy countries distributing additional shots to their populations while poorer nations cannot vaccinate even their most vulnerable citizens.

Despite the criticism, the Biden Administration hopes that giving more vulnerable Americans additional doses will help boost long-term protection against severe disease, hospitalization and death as the virus continues to mutate.