Pfizer says a booster dose of its COVID-19 vaccine appears to offer important protection against the new omicron variant.

Pfizer and its partner BioNTech tested how well vaccine-produced antibodies could neutralize omicron in lab dishes. They found significant weakening after the standard two doses.

A booster dose increased antibody levels by 25-fold. The companies said two doses still may protect against severe illness, but they are working to develop an omicon-specific vaccine in case it’s needed.

They announced the findings Wednesday in a press release. The data is preliminary and hasn’t undergone scientific review.