Studies find boosters targeting Omicron not much better than originals

Omicron-specific booster shots from Moderna and Pfizer weren’t significantly better than the original COVID-19 boosters from both drug companies in two small studies that compared how they fared against the most common variants circulating in the United States. Both the original and latest boosters caused antibodies in the human body to surge to fight off the dominant coronavirus variant, BA.5. The newer shots performed marginally better, but researchers said it probably wouldn’t make a difference. The studies by researchers from Beth Israel Deaconess Medical Center, Columbia University, and the University of Michigan are the first to compare the original messenger RNA boosters against the newly authorized “bivalent boosters” in human blood samples. Bivalent boosters, which also rely on mRNA technology, target the original strain and the BA.4/BA.5 Omicron variants. Federal regulators, alarmed by the spread of breakthrough COVID cases in people who received the original mRNA shots, cleared Omicron-specific boosters in the late summer based only on safety and efficacy data in animals, in what was considered a controversial move. But uptake of the new boosters has been slow. According to the Centers for Disease Control and Prevention, only about 19.4 million Americans, or nearly 6 percent of the US population, have received a bivalent booster since they were approved on Aug. 31. The Beth Israel study compared the immune responses in blood samples taken from 15 people who received the original booster with 18 people who received the bivalent booster. Both the new and old booster shots raised antibody levels against BA.5. The new booster led to 30 percent higher antibody levels, but that difference was “modest and nonsignificant,” said the study, which was posted Tuesday. A Moderna spokesman said the Cambridge-based drug firm expects to have results of the company’s own analysis of how well its bivalent vaccine performs against BA.4/BA.5 later this year and had no comment “on research we were not involved in.” Dr. David Ho’s lab at Columbia University and Aubree Gordon’s lab at the University of Michigan compared antibodies in blood samples from 19 people who received the original boosters with antibodies in 21 people who received the new boosters. In their study, which was posted on a server on Monday, the Omicron booster triggered 20 percent higher antibody levels to BA.4/BA.5 than the original booster. — JONATHAN SALTZMAN and RYAN CROSS