The federal authorities’s call for a pause on utilizing Johnson & Johnson’s coronavirus vaccine may final not less than one other week, additional complicating efforts by federal and state well being officers to reschedule appointments, and reassure jittery People that the vaccine is secure and efficient.

The Facilities for Illness Management and Prevention’s unbiased vaccine advisory panel, often called the Advisory Committee on Immunization Practices, or ACIP, has been scheduled to fulfill for a second time since photographs have been halted, subsequent Friday, to debate security information associated to a small variety of blood-clotting instances in Johnson & Johnson vaccine recipients. It is unclear whether the vaccine was responsible for the clots.

The general public, six-hour assembly may conclude with a vote, for instance, to advocate to proceed the pause, to switch the F.D.A.’s authorization of the single-dose vaccine or to rescind the pause altogether. The federal authorities may then act rapidly to observe the steerage.

“We acknowledge the crucial significance of transferring rapidly. That’s why we may have two unscheduled ACIP conferences in a 10-day interval,” Dr. Rochelle P. Walensky, the C.D.C. director, stated at a White Home information convention Friday.

She stated that the C.D.C. had contacted over 10,000 suppliers “to make sure that they know what sorts of instances to search for.”

The panel’s resolution was a key a part of the federal authorities’s nonetheless principally undefined plan for resolving the pause, which Dr. Janet Woodcock, the performing commissioner of the F.D.A., advised reporters on Tuesday may final solely “a matter of days.” However the panel of professional advisers, whose suggestions carry important weight with state well being departments and physicians, decided Wednesday to wait on a vote whereas they take extra time to evaluate a attainable hyperlink to the uncommon however severe blood-clotting dysfunction.

Dr. Anthony S. Fauci, the federal government’s prime infectious illness professional, advised lawmakers at a listening to on Thursday that “hopefully we’ll get a choice fairly quickly as as to if or not we will get again on observe with this very efficient vaccine.” State well being departments have rescheduled appointments and substituted two-dose vaccines made by Pfizer-BioNTech and Moderna — a plan that White Home officers have referenced as a fast solution to make up for the hole.

Whereas Johnson & Johnson’s vaccine has accounted for a fraction of U.S. vaccinations, it has been a key instrument within the Biden administration’s technique. The shot may be stored at regular refrigeration temperatures for 3 months, and at one dose, allowed for individuals to dispense with vaccination in a single go. Some public well being officers fear the pause may deepen hesitancy. And there are considerations about the risks posed to the global vaccination drive in international locations that may sick afford to be explicit about photographs.

In america, the pause has had immediate and dire consequences for local officials, who’ve labored to vaccinate susceptible populations with the shot: homeless individuals in Baltimore, homebound residents within the District of Columbia, the poor and uninsured in Massachusetts and rural residents in numerous states.

In New York Metropolis, Mayor Invoice de Blasio stated Friday on WNYC that the town’s total vaccination marketing campaign had not been derailed by the pause, however the biggest disruption had been to the town’s program for homebound individuals, which relied on the Johnson and Johnson vaccine and has floor to a halt for now.

The town estimated that there are 23,000 homebound candidates for this system, and stated that its vaccination groups have to this point made 3,600 visits. The trouble has been ramping up, and has been lately vaccinating 1,200 individuals per week. On every go to, this system permits for the homebound senior to get the shot, together with anybody else within the family who’s eligible. Mr. de Blasio stated that he hoped the town would once more have the ability to use the Johnson & Johnson vaccine for that inhabitants, but when not, this system would proceed with the opposite licensed vaccines.

About 7.8 million People have received the Johnson & Johnson shot, with round 10 million doses at present unused.

Setbacks with the vaccine, together with a mix-up in a Baltimore plant that lately contaminated as much as 15 million doses of it, have induced the White Home to revise its math in projecting when the nation may have sufficient doses to cowl each American grownup, which President Biden had predicted would occur by the tip of Could.

The White Home press secretary, Jen Psaki, stated on Thursday that there could be sufficient doses to cowl 80 p.c of the grownup inhabitants by that time, or seemingly sufficient for each grownup who needs one. She added that there could be sufficient for 90 p.c of the inhabitants by the tip of July.

Sheryl Homosexual Stolberg, Daniel E. Slotnik and Sharon Otterman contributed reporting.