Moderna said on Wednesday it is asking the Food and Drug Administration to evaluate its COVID-19 vaccine for use in a booster shot. The drugmaker’s own testing found that a third shot created “robust antibody responses” to the Delta variant, which is spreading across the U.S.

Moderna also plans to submit data to the European Medicines Agency and other regulatory authorities around the world in the next few days. 

The biotech company’s submission the FDA comes as the Biden administration recommends that most Americans get a booster shot eight months after their second dose of a COVID-19 vaccine. Once the vaccines are fully approved by the FDA and signed off by the Centers for Disease Control and Prevention, the boosters could be administered. 

Last month, the CDC released data that warned of a “significant decline” in vaccine effectiveness against infection from COVID-19 in nursing home residents, raising concerns about waning protection for vulnerable populations. In its statement, Moderna said a third dose of 50 micrograms was tested in people six months after they had received their second vaccination.  

“Our submission is supported by data generated with the 50 [microgram] dose of our COVID-19 vaccine, which shows robust antibody responses against the Delta variant,” said Stéphane Bancel, CEO of Moderna, in the statement. 

Another pharmaceutical firm, Johnson & Johnson, said last week that a second shot of its vaccine eight months after the initial dose was found in a study to promote a “rapid and robust” increase in antibodies in people ages 18 to 55 and in those 65 years and older.

Some pharmacies are already offering third shots to people who are immunocompromised and may need more protection against the coronavirus. Experts from the Department of Health and Human Services said the booster shots may start the week of September 20 for people who had received their second shots eight months earlier.

About 1 in 4 people who have heard about booster shots are concerned about waning vaccine protection, the Kaiser Family Foundation found in a recent survey.