The Food and Drug Administration (FDA) has cleared the booster shots of the Johnson & Johnson and Moderna COVID-19 vaccines.

On Wednesday night (Oct. 20), the FDA gave emergency use authorization for a half dose of Moderna’s booster vaccine for those who have been fully vaccinated for at least six months, at least 65, at high risk of severe COVID-19 or have frequent occupational or institutional exposure to the virus. The federal agency also authorized the Johnson & Johnson booster shot. “The use of a single booster dose of the Janssen (Johnson and Johnson) COVID-19 Vaccine may be administered at least 2 months after completion of the single-dose primary regimen to individuals 18 years of age and older,” the FDA said in a statement.

The FDA also stated that any of the approved booster vaccine shots, including Pfizer, could be used in a “mix and match” approach. “The use of each of the available COVID-19 vaccines as a heterologous (or ‘mix and match’) booster dose in eligible individuals following completion of primary vaccination with a different available COVID-19 vaccine,” the FDA said.

“Today’s actions demonstrate our commitment to public health in proactively fighting against the COVID-19 pandemic,” Dr. Janet Woodcock, acting FDA Commissioner, said in a statement.

“As the pandemic continues to impact the country, science has shown that vaccination continues to be the safest and most effective way to prevent COVID-19, including the most serious consequences of the disease, such as hospitalization and death,” she added.

The authorization could open up booster shots to more than 15 million people who have received the Johnson & Johnson vaccine and the 69 million people who have received the Moderna vaccine. According to a study published by the National Institutes of Health last week, all three booster shots enhanced antibody levels, however, Moderna’s and Pfizer’s boosters seemed to work best.