CNN  — 

Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, signed off Thursday on the recommendation of the agency’s independent vaccine advisers in favor of updated Covid-19 vaccine boosters from Pfizer/BioNTech and Moderna.

The CDC’s Advisory Committee on Immunization Practices voted 13 to 1 earlier in the day to recommend updated mRNA boosters for Americans this fall.

Walensky’s decision means the shots could be available by Friday, according to pharmaceutical manufacturers, which began shipping the new doses after the US Food and Drug Administration authorized them Wednesday.

“The updated COVID-19 boosters are formulated to better protect against the most recently circulating COVID-19 variant,” Walensky said in a statement. “They can help restore protection that has waned since previous vaccination and were designed to provide broader protection against newer variants. This recommendation followed a comprehensive scientific evaluation and robust scientific discussion. If you are eligible, there is no bad time to get your COVID-19 booster and I strongly encourage you to receive it.”

The updated boosters have instructions that tell our cells to make antibodies against two strains of the virus that causes Covid-19: the original strain and the BA.4 and BA.5 Omicron subvariants, which share the same spike.

Pfizer/BioNTech’s updated vaccine is a 30-microgram dose authorized for people 12 and older. Moderna’s updated vaccine is a 50-microgram dose authorized for people 18 and older.

The CDC said in the statement that it “also expects to recommend updated COVID-19 boosters for other pediatric groups” in the coming weeks.

People are eligible for the updated boosters as long as they have completed all primary doses in their vaccine series. The committee recommended that the new boosters be given at least two months after the last dose of any Covid-19 vaccine and up to three months after an infection.

The new formulations do not replace shots for the primary series.

The boosters were approved based on studies in mice bred to have human ACE-2 receptors – the doors the coronavirus uses to get into our cells – but clinical trial data showing how well they may work in humans won’t be available for another month or two.