Covid-19 booster shots targeting omicron subvariants received approval from the Food and Drug Administration (FDA) this week, and they were recommended Thursday by the director of the Centers for Disease Control and Prevention (CDC), clearing the way for shots to go into arms within days.
“As we head into fall and begin to spend more time indoors, we strongly encourage anyone who is eligible to consider receiving a booster dose with a bivalent Covid-19 vaccine to provide better protection against currently circulating variants,” FDA commissioner Robert Califf says in a statement.
The two new shots, one from Moderna and the other from Pfizer and BioNTech, will be available to anyone who has received their primary or booster dose at least two months ago; neither is meant to be a first vaccination, the FDA says in the statement. Moderna’s formula will be available for anyone 18 years or older, and Pfizer’s will be for those who are 12 or older. The shots, like their earlier counterparts, will be free to the public.
The FDA asked manufacturers to develop boosters targeting the newest omicron subvariants in June, writes Science’s Gretchen Vogel. The shots are “bivalent,” because they’re designed to protect against both the original coronavirus strain and the newer BA.4 and BA.5 omicron subvariants, which are considered the most contagious yet, writes Lauran Neergaard of the Associated Press (AP). The vast majority of new infections are caused by these subvariants—with an estimated 89 percent caused by BA.5 alone, according to the CDC.
Since mid-July, Covid-19 has killed an average of 400 to 500 Americans per day, according to the New York Times. Though cases are currently trending downward, some experts fear a rise in infections during the fall and winter, and the new boosters are meant to control any upcoming surge.
The federal government has already purchased over 170 million doses of the new formulas, per the Washington Post’s Laurie McGinley. Pfizer says it can ship 15 million doses by September 9, and Moderna says it will have shots available nationwide in the coming days, per STAT News’ Matthew Herper.
These new boosters received approval based on trials in mice, but human trial data is still to come. To make its decision, the FDA also considered the safety and effectiveness of past Covid-19 shots, and it took into account human data from a clinical trial earlier this year, which tested other omicron-focused mRNA vaccines. Those vaccines were meant to target the BA.1 subvariant, and they are similar to these new booster formulas, per the FDA statement.
Authorizing the shots without human clinical trial data is not unheard of—in fact, it mirrors the strategy the FDA uses for new influenza vaccines, writes STAT News.
Approaching new Covid-19 boosters in a similar way to flu shots makes sense, Leif Erik Sander, an infectious disease expert at the Charité University Hospital in Germany, tells Science. Getting people updated vaccines as quickly as possible is “an ethical issue,” Sander told the publication. “We need to allow people to protect themselves from a virus that we can’t fully control.”
But Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota, tells the Post that he wishes human data were available right away to help understand whether the immune response from the new boosters is as good as or better than the response from other vaccines. “We don’t have data to support that the BA.4/BA.5 vaccine is superior,” Osterholm says to the Post.
Moderna and Pfizer are conducting human studies as the boosters roll out, per the AP.
Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, tells the Post that the updated boosters will be helpful even if a new variant emerges.
And for the time being, the new boosters “will work better at protecting against omicron” than the current shots do, Andrew Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health, tells the AP. Since people who have previously been infected with omicron can catch Covid-19 again, “you should definitely go for the booster even if you’ve been infected in the last year,” Pekosz tells the publication.
Editor’s note, Sept. 2, 2022: This story was updated to include the CDC’s recommendation of the shots.