Bivalent vaccine effectiveness

[edschweppe]

Well, that's disappointing. A couple of very small studies indicate that the bivalent COVID-19 booster vaccinations aren't significantly more effective that the original vaccines against the Omicron variants:

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.

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"People should realize that the monovalent vaccines that they were getting were already excellent at preventing severe disease, which was the goal," said Dr. Paul Offit, a vaccine expert at Children's Hospital of Philadelphia who wasn't involved in the studies but read them on a pre-print server. "The hope was that you'd have even better protection against severe disease with the bivalent booster. Given these data, it doesn't look like that hope is going to be realized."

Offit, a member of an independent panel of scientific advisers to the US Food and Drug Administration that voted on June 28 to recommend the agency clear the Omicron-specific boosters, was among two panelists who voted "no." He said at the time that he was concerned about the lack of clinical data and wasn't convinced that the new booster was better.

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.

Specialized immune cells called T cells increased only modestly after people got the original or revamped boosters. The overall trend involving immune cells and antibodies was similar regardless of whether people got Pfizer or Moderna boosters.

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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. "To some extent, we were surprised," Ho said. "I don't think 20 to 30 percent more antibodies would make much of a clinical difference."

Both studies have limitations, including the small number of people tested and the lack of long-term follow-up. Both groups measured antibodies about three to five weeks after people received booster shots. "With time or maybe a second bivalent booster there could be a difference, but we would need to do those studies," Ho said. "The new vaccine is certainly not worse, and may prove to be better with time, but we have to wait and see."

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Larissa Thackray, an infectious diseases biologist at Washington University School of Medicine in St. Louis, said larger studies may find that 20 to 30 percent higher antibody levels are significant. But, she said, vaccine makers should focus on developing next-generation COVID vaccines that spur broader and longer-lasting immunity, rather than updating the vaccine to match each new variant.

Neither study looked at more than fifty people, nor did the studies do any longer-term followup. And there's no indication that the bivalents are worse than the original vaccines against severe acute disease and death. So this isn't bad news by any stretch. But it is somewhat disappointing.