- Pfizer and its German partner BioNTech have asked the FDA to authorize updated Covid booster shots that target the omicron BA.4 and BA.5 omicron subvariants.
- The U.S. is planning a fall booster campaign with the new shots amid concerns about another wave of infection.
- Public health officials hope the new shots will provide more durable protection against infection and mild illness, but some experts say not enough data has been presented.
Pfizer and its German partner BioNTech on Monday asked the Food and Drug Administration to authorize Covid booster shots that target the omicron BA.4 and BA.5 subvariants for people ages 12 and older.
The U.S. is preparing for a fall vaccination campaign using updated vaccines that target the dominant omicron subvariants. Public health officials expect another wave of infection this fall and winter as immunity from the currently authorized shots wears off and people head indoors to escape the colder weather.
The updated vaccines would target the original strain of the virus that first emerged in Wuhan, China, in 2019 as well as omicron, known as a bivalent vaccine. Scientists and public health officials hope the new shots will provide broader and more durable protection against infection and mild illness.
The currently authorized shots were developed to target the version of Covid that first emerged in China. Though the original vaccines are still preventing severe disease, they are not providing substantial protection against infection and mild illness.
Dr. Ashish Jha, the White House Covid response coordinator, has said the new shots will become available to the public by early to mid-September. Pfizer said it can ship the omicron BA.4/BA.5 boosters as soon as the FDA authorizes them. The U.S. government has secured 105 million doses of Pfizer's updated shots and 66 million doses of Moderna's new vaccine.
The FDA is working closely with the vaccine manufacturers to ensure the updated Covid boosters are available in the fall after a review of the safety and effectiveness of the shots, according to agency spokesperson Abby Capobianco.
"The agency will work expeditiously to review this and any other submissions once received in order to make modified COVID-19 vaccines available for booster vaccination in this timeframe," Capobianco said.
However, some infectious disease and public health experts are calling for the FDA and the vaccine companies to present more data on the new shots before they receive authorization. It's unclear whether or not the FDA's independent vaccine advisory committee will meet to review more data on the shots before the agency authorizes them.
Publicly available data on the Pfizer's shots that target omicron BA.4 and BA.5 is sparse right now and based on studies in mice. In June, Pfizer presented data to the FDA's independent vaccine advisory committee that showed the bivalent omicron shots increased antibodies in mice that protect against infection by about 2.6 fold compared with the original vaccine.
Dr. Paul Offit, a member of the FDA advisory committee, said it makes sense that a vaccine which includes the omicron subvariants would bolster the immune response in humans. But Offit said data from mice is not enough to demonstrate that is the case. The vaccine companies and the FDA need to present human data to the public that shows a dramatic increase in neutralizing antibodies from the omicron BA.4 and BA.5 shots in people compared with the original vaccine, he said.
"You have to show some evidence in people that the immune response that you're getting with the bivalent vaccine is clearly better, and those data haven't been presented," said Offit, an infectious disease and vaccine expert at Children's Hospital of Philadelphia.
"You can't ask millions of people to get this booster dose without showing some human data that you have a dramatic increase in neutralizing antibodies to the BA.4/BA.5 strains as compared to boosting with the ancestral type," Offit said, referring to the currently authorized shots based on the version of Covid that emerged in Wuhan, China, more than two years ago.
Michael Osterholm, a leading epidemiologist at the Center for Infectious Disease Research and Policy in Minnesota, also said more data needs to be presented on how the BA.4/BA.5 shots perform in humans.
"It's not that I don't think it could work," Osterholm said. "But I think we need the data first to show that the immune response to this vaccine is equivalent to or better than what we have already."
Dr. Peter Hotez, an infectious disease and vaccine expert at Baylor College of Medicine in Texas, said it's worth waiting a little longer for human data on the omicron shots. Hotez led a team that developed a Covid vaccine based on protein technology that is authorized in India.
"I would be surprised if the FDA would move forward on the whole show just based on mouse data alone," Hotez said. "It's just a matter of a few extra weeks to get essentially human data. I think it's worth it because remember, the American people are not rushing to get boosted anyway," he said.
Omicron BA.5 is the dominant strain of Covid circulating in the U.S. right now, making up about 90% of new infections, according to the Centers for Disease Control and Prevention. The omicron BA.4 and BA.4.6 subvariants represent a little more than 10% of new infections taken together. These versions of omicron are more contagious than past variants of Covid.
Pfizer was originally developing a booster that targets the first version of omicron, BA.1, that caused the massive wave of infection over the winter. But omicron has continued to mutate, and the FDA asked the vaccine makers this summer to switch gears and focus on BA.4 and BA.5.