A federal advisory committee of outside experts is meeting Wednesday to help fashion the U.S. coronavirus vaccine strategy for the rest of the year, amid growing evidence that new variants have eroded the power of the existing vaccines.

The panel of the Food and Drug Administration is trying to determine where the United States is headed in its effort to search for reconfigured vaccines that could help better protect against new variants that have emerged over the past six months.

The meeting, which starts at 8:30 a.m. Eastern time, represents a kind of transition point for the federal government, one troubled with many uncertainties. Many scientists have concluded that the existing vaccines need to be retooled to meet the evolving virus. Federal officials are anxious to figure out how to do that as soon as possible, lest the nation confront a scenario when the virus resurges in the fall and the vaccines’ defenses are depleted.

The committee will hear from a cast of luminaries, including experts from the Centers for Disease Control and Prevention, the National Institutes of Health, the World Health Organization and the F.D.A.’s office of vaccine research.

Sharon Alroy-Preis, the director of public health services for Israel’s Health Ministry, will describe Israel’s experience with administering a second booster shot for those ages 60 and older earlier this year.

Relying heavily on Israeli data, the F.D.A. last week authorized a second booster for Americans 50 and older. Dr. Rochelle P. Walensky, the C.D.C. director, has recommended those shots for those 65 and older, and anyone ages 50 to 64 with serious underlying health conditions.

Some immunologists and vaccine experts, including at least one member of the F.D.A.’s expert panel, have said the federal government went too far with too little data. Those complaints are likely to be aired during the discussion of Israel’s experience.