Moderna Reports Its Booster Is Effective Against Omicron

Moderna reported on Dec. 20 that its currently authorized booster dose raises the level of antibodies able to neutralize the Omicron variant.

The company performed preliminary tests to determine how well blood sera from people who had received its booster dose could neutralize a version of the Omicron variant in the lab. Researchers collected sera from 20 people who had received the currently authorized booster—50 µg, which is half the dose authorized in the original two-dose regimen—and from 20 people who had received a full-dose booster of 100 µg. After about a month, the half dose increased antibodies that can neutralize Omicron by 37-fold compared to levels before the booster, while the full dose raised antibodies 83-fold.

The results are encouraging but don’t represent real-world data yet on how well the booster, at either dose, can actually control spread of Omicron or the severity of COVID-19 among people who are boosted and get infected. Those data are coming, as the company and others are trying to answer those questions by studying people who get breakthrough infections.

That means it’s still not clear how the 37-fold increase in antibodies translates into immune protection for people who get the booster. It’s still unknown, for example, whether that increase is enough to restore protection from serious disease back to the same high levels that the original vaccine did against earlier versions of the virus. Public health experts are encouraged, however, that the higher levels of virus-fighting antibodies do restore some of that protection, and against a fast-moving variant like Omicron, they say any boost in protection is critical. Moderna is continuing to study breakthrough infections among people who are boosted, and its scientists are also testing a new version of the vaccine designed to target Omicron specifically.

For now, the new lab results suggest that the current vaccine at the currently authorized dose does appear to bolster people’s ability to mount a response against Omicron. Moderna has not indicated yet whether it will consider submitting a request to the Food and Drug Administration (FDA) to authorize the full dose booster, given the encouraging data so far and the expected surge in Omicron cases this winter.