Moderna's updated COVID-19 vaccine was not more effective at preventing COVID-19 infection, according to a new study.
Researchers funded by Moderna analyzed the updated shot, which contains elements of the Wuhan virus strain and the BA.1 strain, in comparison to the old booster, which was only targeted at the Wuhan variant. They recorded more participants contracting COVID-19 in the group who received the updated booster.
Among those who received the updated shot, 11, or 2.5 percent, contracted COVID-19. Among those who received the old booster, 9, or 2.4 percent, tested positive for COVID-19.
In a breakdown of those without prior COVID-19 infection, more participants in the updated booster group got COVID-19—11, or 3.2 percent—than those who received the old booster—5, or 1.9 percent). None of the volunteers who received the updated booster and had prior infection were re-infected. Three participants with natural immunity were re-infected after receiving the old booster, but none displayed symptoms.
"The incidence of infections was numerically higher in the mRNA-1273.214 group than in the mRNA-1273 group among participants with no previous SARS-CoV-2 infection and balanced between the two groups among all participants owing to reinfections in the mRNA-1273 group," researchers said. "However, the study was not designed to evaluate vaccine effectiveness, and the follow-up time of infection after the booster is limited, which precludes conclusions about protection."
mRNA-1273.214 is the updated booster; mRNA-1273 is the old booster.
Moderna did not respond to a request for comment.
Researchers said the measurements showed a better immune response after the updated booster, which "indicate that bivalent vaccines may be a new tool in the response to emerging variants."
Regulators in a number of countries have cleared the Wuhan-BA.1 booster. In the United States, regulators chose to have Moderna and Pfizer reformulate the shots, replacing BA.1's spike protein with a BA.4/BA.5 one.
BA.1, BA.4, and BA.5 are all subvariants of the Omicron virus variant. BA.5 is the dominant strain in America at present.
The updated boosters from the companies were granted emergency use authorization by the U.S. Food and Drug Administration earlier in September, even though no human data was available. The Centers for Disease Control and Prevention then recommended an updated booster for all Americans 12 and older.
The old boosters are no longer available.