Bivalent booster shots from Moderna and Pfizer failed to raise levels of protective proteins called neutralizing antibodies against the dominant omicron strains any more than four doses of the original COVID-19 vaccines, according to an early independent study on a small group of people.
Researchers at Columbia University and the University of Michigan compared the levels of protective proteins, called 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 the 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.