By BLOOMBERG

Moderna Inc. said a third dose of its Covid-19 vaccine increased antibody levels against the omicron variant, results the company said are reassuring even as it works on a version of its shot tailored to the new strain. 

A 50 microgram booster dose – the authorized amount – saw a 37-fold increase in neutralizing antibodies, the company said in a statement Monday. The company also tested a 100 microgram dose, which increased antibody levels 83-fold compared with the primary two-dose course.

The results are a good sign for the shot as companies race to understand how well their vaccines hold-up against the new variant and assess whether new shots will be required to contain it. Pfizer Inc. and BioNTech SE said earlier this month initial lab studies showed a third dose of their Covid-19 vaccine may be needed to fight the omicron variant after a 25-fold reduction in neutralizing antibodies against the variant was observed in people who got just two shots.

The Moderna data are based on the sera from 20 booster recipients with each dose, with antibody levels measured on day 29 post-boost, the company said. The biotech is also working on an omicron-specific variant vaccine, which it plans to start testing in humans early next year.

The data are “reassuring”, Stephane Bancel, chief executive officer of Moderna, said in a statement, adding: “To respond to this highly transmissible variant, Moderna will continue to rapidly advance an omicron-specific booster candidate into clinical testing in case it becomes necessary in the future.” 

Moderna is testing different booster candidates against a range of variants in mid and late-stage trials. The company has also been testing the safety and tolerability of the higher 100 microgram booster dose. 

The higher dose level was generally well tolerated and the frequency of adverse events similar to those experienced after the primary two-dose course, which is also given at 100 micrograms per shot. There were slightly more frequent side effects from the 100 microgram booster than the 50 microgram third dose, the company said.