With updated formulations apparently close at hand, federal officials have decided against expanding eligibility for second boosters of the existing vaccines this summer. The new versions are expected to perform better against the now-dominant Omicron subvariant BA.5, although the data available so far is still preliminary.

At this point, only Americans over 50 and those over 12 with certain immune deficiencies have been eligible for second booster doses. Although some federal officials pressed to bolster the protection of younger Americans now, officials agreed on the goal of strengthening everyone’s immunity in the fall with what is hoped to be a more effective booster, ahead of a possible winter surge of the virus.

In internal deliberations, some senior health officials argued that eligibility for a second booster should be broadened before the reformulated version is ready because coronavirus infections are on the rise again. Dr. Anthony S. Fauci, the president’s chief medical adviser, and Dr. Ashish K. Jha, the White House pandemic response coordinator, both advocated that position.

“I think there should be flexibility and permissiveness in at least allowing” a second booster for younger Americans, Dr. Fauci said in an interview this month.