Advisers to the Centers for Disease Control and Prevention unanimously voted Thursday to recommend a booster shot of the Pfizer-BioNTech vaccine to people 65 and older who are at a greater risk of developing breakthrough COVID-19 infections.

Members of the CDC's Advisory Committee on Immunization also endorsed booster shots for those in long-term care and voted 13-2 to endorse boosters for people with underlying medical conditions between the ages of 50 and 64. These groups will be eligible for boosters six months after receiving the second vaccine shot.

At least 27 million people who are 65 or older will be eligible for a booster dose.

CDC advisors did not endorse boosters for other high-risk groups, including people at higher risk due to their jobs such as frontline workers.

Meanwhile, advisers to the CDC voted 9-6 to recommend those between the ages of 18 and 49 to get a booster COVID-19 vaccine dose if they have underlying health conditions, CNN reported.

This latest move by the CDC comes a day after the Food and Drug Administration approved a booster shot of the Pfizer-BioNTech vaccine for Americans over the age of 65 who had received previously two doses of the same vaccine brand as well as adults between the ages of 18 and 64 whose jobs put them at risk of contracting severe complications of COVID-19.

The CDC booster shot recommendation only applies to the Pfizer vaccine.