August 22, 2022 1:21 PM EDT

All COVID-19 vaccines that are used in the U.S. target the same original strain of SARS-CoV-2. But boosters designed to protect against the latest Omicron subvariants could be coming soon.

On Aug. 22, Pfizer-BioNTech submitted a request to the U.S. Food and Drug Administration (FDA) to authorize its Omicron-specific vaccine. The shot targets BA.4 and BA.5, which now account for nearly all new infections in the U.S.

In an announcement, Pfizer-BioNTech requested emergency use authorization for a booster dose of the vaccine, which contains a combination of the genetic material mRNA from the original virus circulating when the vaccine was initially approved in August 2021, and mRNA from the newer BA.4 and BA.5 subvariants. The vaccine is intended for anyone 12 years or older.

The companies have been studying the BA.4 and BA.5 vaccine in animal models and submitted that data to the FDA for review. Those studies showed the vaccine was safe and produced a “strong neutralizing antibody response against Omicron BA.1, BA.2 and BA.4/BA.5,” the companies said in the statement. Pfizer-BioNTech says it has scaled up production of the BA.4/BA.5 vaccine and is ready to begin shipping immediately if the FDA authorizes the shot. The FDA has not indicated a timetable for if and when that might happen, but given that the agency requested that vaccine makers develop a BA.4/BA.5 booster in time to protect people in the fall and winter months, when respiratory viruses like SARS-CoV-2 circulate more quickly, the agency will likely act as quickly as possible. If the agency authorizes the booster, the White House’sCOVID-19 response coordinator Dr. Ashish Jha predicted on Aug. 16 that the shot could be available “by early to mid September.”

Data regarding the safety and efficacy of the Omicron-specific vaccine in people are not available yet; those studies in humans are expected to start later in August, the companies said. In addition to the animal data, the request is based on limited human data Pfizer-BioNTech generated with a related vaccine, which targeted another version of the Omicron variant, BA.1. An FDA panel of independent experts reviewed that data in June and decided not to consider it for authorization, and asked the companies to develop a vaccine targeting the BA.4 and BA.5 subvariants instead.

Other vaccine makers are also developing Omicron-specific vaccines and likely won’t be far behind in requesting FDA authorization. Moderna, which makes the other mRNA COVID-19 vaccine approved by the FDA, released promising data in June showing its vaccine, which also targeted the BA.1 subvariant, produced higher levels of virus-fighting antibodies against Omicron in people compared to the original vaccine. At the FDA’s request, Moderna is also developing a BA.4/BA.5-specific version of its Omicron vaccine.

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