In this photo illustration, vials and a medical syringe seen in front of the Food and Drug Administration (FDA) of the United States and Pfizer Pharmaceutical company logos. FDA approves Pfizer/BioNTech the COVID-19 coronavirus vaccine for emergency use in the US, reportedly by media.
Pavlo Gonchar | AP
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 as as immunity from the currently authorized shots wanes 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.
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.
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.
Data on the shots that target omicron BA.4 and BA.5 is sparse right now and is 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 to 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 to 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 because right now, 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.
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