Analysis: The next COVID booster shots will likely be updated for Omicron

NEW YORK, June 24 (Reuters) - COVID-19 vaccines this fall are likely to be based on the Omicron variant of the coronavirus rather than the original strain, although some experts suggest they may only offer significant benefits for older and immunocompromised people.

Moderna (MRNA.O), Pfizer (PFE.N) and Novavax (NVAX.O) have been testing vaccines based on the first BA.1 Omicron variant that became dominant last winter, driving a massive surge in infections.

On Wednesday, Moderna said its updated vaccine worked well against more recent Omicron subvariants, and that it was moving forward with plans to ask regulators for approval. 

Vaccines that can bridge the gap between the original version of coronavirus and the Omicron variant would likely be "far, far better" for the fall, according to Trevor Bedford, a biologist at the University of Washington who has closely tracked mutations of the SARS-coV-2 virus.

Bedford said it would take too long to meet regulatory requirements for a switch to tailor the next vaccine to versions of Omicron spreading quickly now.

"Catching up to any of the Omicrons is really important," he said, noting the enormous jump in the number of mutations from the original strain that emerged in China to Omicron on the spike protein part of the virus the vaccines target.

The World Health Organization (WHO) plans to assess the effectiveness of vaccines built for Omicron, as do national health regulators like the U.S. Food and Drug Administration.