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Why ‘mouse data’ may determine the next round of COVID-19 booster shots

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Syringes loaded with the Pfizer COVID-19 vaccine at a drive-thru COVID-19 vaccination clinic in Farmington.

Syringes loaded with the Pfizer COVID-19 vaccine lie ready for use at the drive-thru COVID-19 vaccination clinic at the Legacy Events Center in Farmington on Jan. 19, 2022.

Laura Seitz, Deseret News

New COVID-19 booster shots now targeting the dominant omicron versions of the virus could be available as soon as September to anyone 12 and older.

Pfizer, along with BioNTech, announced Monday authorization is being sought from the U.S. Food and Drug Administration and the Centers for Disease Control and Prevention for the new booster doses. The companies said the shots will be ready to be shipped immediately upon federal approval.

Pfizer’s booster shots are formulated against the BA.4 and BA.5 subvariants of omicron, the highly transmissible COVID-19 variant that surged through Utah and the rest of the country last winter, driving cases to record levels and straining hospitals.

The CDC estimates BA.5 makes up almost 89% of the nation’s coronavirus cases, while BA.4 and BA.4.6 account for nearly all of the rest. In the region that includes Utah, BA.5 is even more dominant, responsible for an estimated 92.5% of all cases, according to the CDC.

In June, an independent panel of FDA experts recommended the next round of COVID-19 boosters focus on fighting BA.4 and BA.5, which are even more transmissible than the original omicron, even though vaccine manufacturers had already reported test data from shots going after the original omicron.

That’s created some controversy, since the White House goal of getting Americans another booster shot this fall to prevent severe disease from COVID-19 means federal authorities will have to rely on the results of studies involving mice rather than humans.

Pfizer’s announcement about the approval submission said a clinical study to assess the updated formulation’s safety and effectiveness in people 12 and older isn’t expected to start until sometime this month, noting a previous trial of the shots targeted at the original omicron showed “a superior immune response” against that strain.

The vaccine for the original omicron was also described as “well-tolerated with a favorable safety profile.”

Supporters of the federal government’s strategy say the country can’t wait for the human studies to be completed and that there’s already been enough experience with the vaccines to be confident of their safety, according to a recent NPR report.

“We have 500 people a day dying of coronavirus right now. Those numbers sadly might very well rise in the fall and the winter. The question is: ‘Can we do something better?’” Dr. Ofer Levy, a pediatrics and infectious disease researcher at Harvard Medical School who also advises the FDA, told NPR. “And I think the answer is: ‘We can, by implementing this approach.’”

But John Moore, an immunologist at Weill Cornell Medicine in New York, disagrees.

“For the FDA to rely on mouse data is just bizarre, in my opinion,” Moore told NPR. “Mouse data are not going to be predictive in any way of what you would see in humans.”

On Tuesday, Moderna, maker of the nation’s other COVID-19 vaccine that utilizes new mRNA technology, announced that it, too, is seeking authorization for new booster shots for those 18 and older that target both the original strain of COVID-19 as well as the BA.4 and BA.5 omicron subvariants.

The company said in a news release that the application to the FDA “is based on preclinical data” for the new booster shots as well as clinical trial data from a study of a previous formulation that targeted the original omicron strain that showed “potent neutralizing antibody responses against the omicron subvariants BA.4 and BA.5.”