A preliminary study made public Wednesday studied blood samples in the lab from 30 people who had gotten two Moderna shots, and it found that the antibodies in their blood are at least about 50 times less effective at neutralizing the omicron variant of the coronavirus.

Previous research had indicated the Pfizer-BioNTech vaccine is also less protective against omicron. //

But there was good news too. An additional 17 people in the study had received a Moderna booster. And the antibodies in their blood were highly effective at blocking the omicron variant — essentially about as effective as they are at blocking the delta variant, Montefiori says.