SAN JOSE, Calif. — New research by a team of San Francisco scientists is raising questions about the usefulness of a new omicron-specific COVID vaccine for next fall, as the virus quickly evolves and the risk of illness is likely to soar. The study,published in the journal Nature, offers growing evidence that federal policymakers must make a tough choice: Should today’s vaccine be changed – and, if so, how? Time is tight, so a decision is planned next month. It comes as the nation is in the midst of a new wave of infections related to new omicron variant subtypes, averaging more than 105,000 n…