By Michael Erman NEW YORK (Reuters) – Pfizer Inc and BioNTech SE said on Saturday that a booster dose of updated versions of their COVID-19 vaccine, modified specifically to combat the Omicron coronavirus variant, generated a higher immune response against that variant. Advisors to the U.S. Food and Drug Administration are scheduled to meet on Tuesday to discuss whether to update COVID-19 vaccines for the fall. The updated shots are likely to be redesigned to combat the Omicron variant of the coronavirus, experts say. Pfizer and BioNTech said that 30 and 60 microgram doses of a shot targeting …