By Robert Langreth

Bivalent booster shots from Moderna Inc. and Pfizer Inc. failed to raise levels of protective proteins called neutralizing antibodies against the dominant omicron strains any more than four doses of the original Covid vaccine, according to an early independent study on a small group of people.

Researchers at Columbia University and the University of Michigan compared levels of neutralizing antibodies in blood samples from 21 people who got a fourth shot of the Moderna or Pfizer-BioNTech SE bivalent boosters against antibody levels in 19 people who got four shots of the original vaccines.

Three to five weeks after a fourth shot, those people who received the new boosters aimed at BA.4 and BA.5 variants “had similar neutralizing antibody titers as those receiving a fourth monovalent mRNA vaccine,” the authors conclude in a manuscript posted on the preprint server bioRxiv.org. This held true for antibodies that protect against BA.4, BA.5 and older variants such as the original omicron strain, according to the study.

Moderna shares rose 2.7% to $136.57 at the close in New York trading. Pfizer stock was little changed.

The results don’t mean that getting a bivalent shot has no benefit, and it will need to be confirmed in much larger studies. However, they raise the question of whether the switch to a new version of the vaccine was necessary.

The results also contrast sharply with an Oct. 13 press release from Pfizer and BioNTech touting “positive early data” from a clinical trial suggesting that its bivalent vaccine “is anticipated to provide better protection.” The statement was based on data collected from subjects in the first seven days after immunization, and the company has not yet released details.

“Little difference in antibody levels is shown between a bivalent booster and the original shots, potentially opening the door to competing vaccines from the likes of Sanofi and GSK.”

“So far we don’t see the benefit” of the bivalent shots over the old ones, said study senior author David Ho, a virologist who heads the Aaron Diamond AIDS Research Center at Columbia University. A clear difference between the boosters could emerge over longer periods of time, he said in a telephone interview. It could also turn out that a second booster shot with the bivalent vaccine may be needed, he said.

Ho said that the study has been submitted for publication in a scientific journal.

Slow Rollout

Rollout of the bivalent vaccines has been slow so far. Only about 20 million Americans have received the latest version of the vaccine, according to the Centers for Disease Control and Prevention.

The lackluster results for bivalent boosters could be due to a phenomenon called imprinting, Ho said. That means that the immune system most strongly remembers the first version of a virus it encounters. After it mutates, the response to a vaccine -- even one targeting newer strains -- may still be tilted toward fighting the original pathogen.

Ho said he personally has gotten four doses of the original generation of mRNA shots, and that he is waiting for more data to roll in to decide what to do about a fifth dose.

Pfizer declined to comment on outside research. A spokesperson said the company would reveal additional 30-day data on its bivalent shot in the coming weeks. Moderna didn’t immediately respond to a request for comment.

In early October, Moderna researchers published data from the clinical trial of a different bivalent booster that is tailored to the original omicron strain. That study, found that a fourth shot of that bivalent vaccine produced higher levels of antibodies compared to four shots of Moderna’s original vaccine. Moderna’s bivalent vaccine against the original omicron strain, called mRNA-1273.214, is not authorized in the U.S., but has been cleared for use in numerous countries including the UK and Canada.

Nonetheless, scientists have harbored doubts about the benefit of switching up the shots’ composition. Before the US began rolling out updated boosters in September, John Moore, a professor of microbiology and immunology at Weill Cornell Medical College said the new vaccines would be “little or no better” than earlier formulations.