The Centers for Disease Control and Prevention (CDC) reports the number of seniors who received a booster shot of the COVID-19 vaccine since it became available is over 10 million. 

New data shared by the agency shows that about 10.7 million, or 14.7%, of U.S. seniors over the age of 65, have received a booster since it was authorized for use by the Food and Drug Administration (FDA) on Sept. 22. 

Seniors are the most vaccinated group of people in the U.S. with 84.4% of those over 65 being fully vaccinated against the virus. 

A campaign to deliver booster shots to more Americans has been well underway since September, when the Biden administration launched a new vaccination drive. It was delayed by internal disagreements over insufficient vaccine supplies and data, but the administration has been intent on increasing overall protection against the COVID-19 Delta variant. 

On Oct. 20, the CDC’s Advisory Committee on Immunization Practices is due to meet for a discussion to make a decision on whether or not to endorse boosters for Moderna and Johnson & Johnson vaccines. 

Last week, an FDA advisory panel announced that it endorsed the approval of a lower dose booster from Moderna. The agency, however, offered only a mixed review for Johnson & Johnson’s vaccine, citing insufficient data received from the company. 

An alternative to “mix-and-match” vaccines from different manufacturers is also now on the table. On Tuesday, it was reported that the FDA is expected to share its decision on whether or not to endorse the idea this week.

A study from the National Institutes of Health (NIH) last week found that mixing vaccines could raise the number of antibodies in the immune system to ward off COVID-19.