Pfizer has asked the FDA to authorize a second booster dose of its COVID-19 vaccine for people 65 and older.
The FDA is expected to make a decision before fall to support a potential vaccine campaign as the country heads back into winter.
Multiple other countries, including Israel, Germany, Sweden, and the UK have either begun or announced second booster dose campaigns.
Medical researchers are split on whether the additional doses are needed, when they should be given, and who exactly should receive them. Trial data showing the effectiveness of a fourth dose is limited with mixed results.
Pfizer says its request for approval is based on two real-world studies from Israel that showed a lower rate of infections and lower rate of severe disease. But the company is still trying to quantify exactly how much protection a fourth dose provides.
According to the CDC, about 65% of the US population is vaccinated with two doses. About 44% of those people have received a booster shot.