By Michael Erman (Reuters) -U.S. regulators plan to decide by early July whether to change the design of COVID-19 vaccines this fall in order to combat more recent variants of the coronavirus, with hopes of launching a booster campaign by October, a top Food and Drug Administration official said on Tuesday. “The better the match of the vaccines to the circulating strain we believe may correspond to improve vaccine effectiveness, and potentially to a better durability of protection,” Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said at a meeting of outsid…