Johnson & Johnson vaccine
Johnson & Johnson vaccineReuters

The US Food and Drug Administration (FDA) on Wednesday authorized booster doses of the COVID-19 vaccines from Moderna and Johnson & Johnson, Reuters reported.

In addition, the FDA said Americans can use the “mix and match” method and choose a different shot than their original inoculation as a booster.

"The availability of these authorized boosters is important for continued protection against COVID-19 disease," Acting FDA Commissioner Janet Woodcock said in a statement. She noted that data suggests vaccine effectiveness may wane over time in some fully vaccinated populations.

The decision paves the way for millions more people in the United States to get the additional protection with the highly contagious Delta variant of the virus causing breakthrough infections among some who are fully vaccinated.

Last week, the FDA’s advisory panel unanimously voted to recommend booster shots of Moderna's COVID-19 vaccine for Americans aged 65 and older and those at high risk of severe illness or occupational exposure to the virus.

A day later, the panel also voted in favor of a second shot of Johnson & Johnson's COVID-19 vaccine.

The FDA cleared the Johnson & Johnson COVID-19 vaccine, which works with just one dose instead of two, in late February.

Last month, the FDA authorized a booster dose of the Pfizer and BioNTech vaccine for older adults and some Americans at high-risk of illness.

FDA officials had suggested last week that they were considering lowering the recommended age for booster shots of the Pfizer/BioNTech vaccine to as young as 40, based on data from Israel, where Pfizer booster shots have already been administered broadly.

They did not lower the age range for the shots on Wednesday, but said that they were assessing the benefits and risks of broader use of boosters and plan to update the public in the coming weeks.

A US source told CNN on Tuesday that the US government likely will soon recommend booster shots to people as young as 40.

The source added that there is “growing concern within the FDA” that US data is beginning to show hospitalizations among people under age 65 who have been fully vaccinated.