People who have received the company’s one-shot vaccine may benefit from a booster with another brand. F.D.A. advisers will discuss the data on Friday.People who received a Johnson & Johnson coronavirus vaccine may be better off with a booster shot from Moderna or Pfizer-BioNTech, according to preliminary data from a federal clinical trial published on Wednesday.That finding, along with a mixed review by the Food and Drug Administration of the case made by Johnson & Johnson for an authorization of its booster, could lead to a heated debate about how and when to offer additional shots to the 15 million Americans who have received the single-dose vaccine.The agency’s panel of vaccine advisers will meet Thursday and Friday to vote on whether to recommend that the agency allow Moderna and Johnson & Johnson to offer booster shots.Despite the questions raised by the new data on the strength of Johnson & Johnson’s boosters, some experts anticipated that the agency would clear the shots anyway, since the effectiveness of the one-shot vaccine is lower than that of the two-dose mRNA vaccines made by Moderna and Pfizer-BioNTech. And the broader public may also be expecting the authorizations, given the Biden administration’s push for boosters from all brands.Once the agency authorized a booster from Pfizer-BioNTech last month, “the die was cast,” said John Moore, a virologist at Weill Cornell Medicine.The Pfizer and Moderna vaccines are by far the most used in the United States, with more than 170 million people in the United States fully immunized with either one or the other vaccine. When Johnson & Johnson’s was authorized in February, public health experts were eager to deploy the “one-and-done” option, particularly in communities with poor access to health care. But the shot’s popularity plummeted when the F.D.A. later paused its use to investigate rare blood clotting cases.For those who have received the Johnson & Johnson vaccine, the timing of a booster authorization — of any brand — is still uncertain. The F.D.A. panel is set to vote Friday only on whether the agency should permit a second dose of the Johnson & Johnson vaccine, a scenario the Centers for Disease Control and Prevention’s own vaccine advisory committee will discuss next week. If both agencies believe an additional dose should be offered, people could seek them out as early as next week.Whether the F.D.A. might authorize the mix-and-match approach, and how, is unclear. The strategy will be discussed at the agency panel’s meeting on Friday, but no vote will be taken. If regulators eventually believe there is enough scientific support for the approach, they would likely need to update the authorization language of the Moderna and Pfizer-BioNTech vaccines to allow for their use in people who initially received Johnson & Johnson’s.In a study conducted by the National Institutes of Health, researchers organized nine groups of roughly 50 people each. Each group received one of the three authorized vaccines, followed by a booster. In three groups, volunteers received the same vaccine for a boost. In the other six, they switched to a different brand.The researchers found that those who got a Johnson & Johnson shot followed by a Moderna booster saw their antibody levels rise 76-fold within 15 days, whereas those who received another dose of Johnson & Johnson saw only a fourfold rise in the same period. A Pfizer-BioNTech booster shot raised antibody levels in Johnson & Johnson recipients 35-fold.The authors cautioned about the study’s small size and noted that they did not follow the volunteers long enough to identify rare side effects.Scott Hensley, an immunologist at the University of Pennsylvania who was not involved in the new study, found the results compelling. He noted, however, that the trial only looked at antibody levels, which on their own are an insufficient measure of how well different combinations of vaccines would lower Covid-19 infections and hospitalizations.“At the end of the day, folks having the Johnson & Johnson should probably get an mRNA booster,” he said. “It’s just a matter of, how much data does the F.D.A. need before making that recommendation?”“I wouldn’t want to be in their shoes,” he added.Some scientists question how the federal government is considering boosters of any brand, given the limited data provided not only by Johnson & Johnson, but the other companies as well.“There are some of us who would really like to see more data,” said Dr. Celine Gounder, an infectious disease specialist at Bellevue Hospital Center in New York. “And then there are others who want to just move forward on boosters.”A pop-up Covid vaccine clinic at a high school in Albuquerque, N.M., this summer.Paul Ratje for The New York TimesEarlier on Wednesday, an F.D.A. analysis questioned a key test used by the company, known as a psVNA assay, saying it may have skewed the findings.“It is likely that the results seen are due to the low sensitivity of the psVNA assay used,” the F.D.A. stated in its report. The regulators also said that they didn’t have enough time to independently review much of the raw data from the company’s trials.The F.D.A. did see a potential improvement in protection from a Johnson & Johnson booster given two months after the first shot, based on a large trial sponsored by the company. Some scientists have contended that its vaccine should have been a two-dose shot from the beginning.“Although not independently confirmed by F.D.A. from data sets, summaries of the data suggest there may be a benefit in a second dose administered approximately two months after the primary dose,” the agency said in its report.Johnson & Johnson in a statement said it looked forward to discussing the data on Friday, when panelists will also hear a presentation on the mix-and-match study..css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-k59gj9{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;width:100%;}.css-1e2usoh{font-family:inherit;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;border-top:1px solid #ccc;padding:10px 0px 10px 0px;background-color:#fff;}.css-1jz6h6z{font-family:inherit;font-weight:bold;font-size:1rem;line-height:1.5rem;text-align:left;}.css-1t412wb{box-sizing:border-box;margin:8px 15px 0px 15px;cursor:pointer;}.css-hhzar2{-webkit-transition:-webkit-transform ease 0.5s;-webkit-transition:transform ease 0.5s;transition:transform ease 0.5s;}.css-t54hv4{-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-1r2j9qz{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-e1ipqs{font-size:1rem;line-height:1.5rem;padding:0px 30px 0px 0px;}.css-e1ipqs a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;}.css-e1ipqs a:hover{-webkit-text-decoration:none;text-decoration:none;}.css-1o76pdf{visibility:show;height:100%;padding-bottom:20px;}.css-1sw9s96{visibility:hidden;height:0px;}.css-1in8jot{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;font-family:’nyt-franklin’,arial,helvetica,sans-serif;text-align:left;}@media (min-width:740px){.css-1in8jot{padding:20px;width:100%;}}.css-1in8jot:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1in8jot{border:none;padding:10px 0 0;border-top:2px solid #121212;}What to Know About Covid-19 Booster ShotsThe F.D.A. authorized booster shots for a select group of people who received their second doses of the Pfizer-BioNTech vaccine at least six months ago. That group includes: Pfizer recipients who are 65 or older or who live in long-term care facilities; adults who are at high risk of severe Covid-19 because of an underlying medical condition; health care workers and others whose jobs put them at risk. People with weakened immune systems are eligible for a third dose of either Pfizer or Moderna four weeks after the second shot.Regulators have not authorized booster shots for recipients of the Moderna and Johnson & Johnson vaccines yet, but an F.D.A. panel is scheduled to meet to weigh booster shots for adult recipients of the Moderna and Johnson & Johnson vaccines.The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.It is not recommended. For now, Pfizer vaccine recipients are advised to get a Pfizer booster shot, and Moderna and Johnson & Johnson recipients should wait until booster doses from those manufacturers are approved.Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.The F.D.A.’s discussion this week of the Johnson & Johnson vaccine has big implications for the shot’s future in the United States, said Jason L. Schwartz, an associate professor of health policy at the Yale School of Public Health. The vaccine was already unlikely to gain more acceptance in the country in the long run, he said. And if the F.D.A. ultimately recommends a booster shot for Johnson & Johnson recipients of a different vaccine, he added, “it’s hard to see what would steer people to the J.&J. vaccine.”The F.D.A. has already authorized an additional shot of the Pfizer-BioNTech vaccine for people older than 65 years, or those 18 to 65 with underlying health conditions or job exposures that put them at higher risk. Moderna’s application, which will be discussed on Thursday, may also win authorization, despite limited evidence that the protection provided by the initial two-dose regimen of Moderna is waning.Regulators on Wednesday wrote that a single shot of the Johnson & Johnson vaccine “still affords protection against severe Covid disease and death in the United States.” But they also said that the highest estimates of protection, including for severe Covid, were “consistently less than the highest effectiveness estimates” for the Moderna and Pfizer-BioNTech shots.Both Moderna and Pfizer booster shots showed significant increases in antibody levels after 15 days in the new study, much more than Johnson & Johnson’s.Brittainy Newman for The New York TimesA clinical trial showed that one dose of J.&.J. had an efficacy rate of 66 percent against moderate to severe Covid worldwide, and 74 percent in the United States. Its efficacy against either severe or critical disease was stronger, at 85 percent worldwide.In its application for a booster, Johnson & Johnson included the results of another large-scale trial that began in November 2020, in which they gave half their volunteers a second dose two months after the first. The other half received a placebo.In August, the company announced that in the portion of the trial that took place in the United States, the efficacy rose to 94 percent. But in its report, the F.D.A. focused on the worldwide results, in which the increase was more modest, rising to 75 percent.Dr. Hensley cautioned that the efficacy estimates from the trials had a fairly wide range of uncertainty. “What that tells you is that the slight changes in effectiveness here might be due to chance,” he said.Against severe to critical Covid disease, two shots had an efficacy of 100 percent. But regulators warned in the analysis posted Wednesday that there was little data from that trial on the Delta variant, which now causes the vast majority of infections in the United States.The emphasis on enhancing Johnson & Johnson’s vaccine with a second shot “reflects the fact that our booster conversation has shifted in recent weeks to not just preventing severe cases, hospitalizations and deaths. It has shifted to how we prevent infections, period,” Dr. Schwartz said. “J.&J. was lagging behind from the beginning.”In August, when top Biden administration health officials announced plans to possibly begin administering booster shots in September to Moderna and Pfizer-BioNTech recipients, they said they anticipated that those who received Johnson & Johnson’s shot would also need one, though more data was needed.That announcement “set unreasonable expectations” for those who had received Johnson & Johnson’s vaccine, Dr. Schwartz said, and “made the J.&J. conversation even that much more confusing.”Sharon LaFraniere contributed reporting from Washington.

In a new analysis, the Food and Drug Administration questioned the strength of evidence Johnson & Johnson provided in its application for booster shots. A key test used by the company was likely not sensitive enough, the agency suggested, adding that it didn’t have enough time to independently review much of the raw data from the trials.The document, released in advance of a Friday meeting of the agency’s vaccine advisers, could have significant influence on whether the 15 million Americans who have received the one-dose vaccine will be allowed to get a second shot, or if they will instead be urged to get a different brand of vaccine for added protection.The authors of the report did not take a position on whether the agency should approve Johnson & Johnson’s application, and it was unclear whether the flaws they identified in the data would be considered significant enough to deny the authorization.The agency’s analysis follows a report released on Tuesday, in which Johnson & Johnson argued in favor of a booster, presenting data from a number of trials.“A booster dose is recommended at 6 months or later, based on the strength of the immune responses,” the company wrote.But on Wednesday, the F.D.A. said that the test used by the company to measure the immune response of a six-month-boost — known as a psVNA assay — is not sensitive enough for the task. The agency also questioned whether the increase in immune response was as big as the data suggested.“It is likely that the results seen are due to the low sensitivity of the psVNA assay used,” the F.D.A. stated in its report. Regulators warned that it was difficult to compare results from the company’s six-month and two-month booster studies as a result.The F.D.A. saw a potential improvement in protection from a J. & J. booster given two months after the first shot, based on a large trial sponsored by the company.“Although not independently confirmed by F.D.A. from datasets, summaries of the data suggest there may be a benefit in a second dose administered approximately 2 months after the primary dose,” the agency said in its report.The fact that the F.D.A. had not independently confirmed key data was a departure from past briefing documents for other vaccines. The F.D.A. said that it didn’t have time to vet much of Johnson & Johnson’s material before the meeting later in the week.The agency scheduled the meeting of its outside advisers before the company had even submitted its application for a booster dose — an unusual move, some public health experts said.“Except where noted, datasets were not submitted in sufficient time for FDA to conduct an independent review to verify the Sponsor’s analyses,” the F.D.A. said in its report.A spokesman for Johnson & Johnson did not immediately respond to a request for comment.The F.D.A. has already authorized an additional shot of the Pfizer-BioNTech vaccine for people over 65 years of age, or with health conditions or job exposures that put them at higher risk. Moderna has also submitted an application for a booster which will be evaluated by the F.D.A.’s advisers on Thursday. It may also win authorization, despite limited evidence that the protection provided by an initial two doses of Moderna is waning..css-1kpebx{margin:0 auto;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-1kpebx{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-1kpebx{font-size:1.25rem;line-height:1.4375rem;}}.css-1gtxqqv{margin-bottom:0;}.css-k59gj9{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;width:100%;}.css-1e2usoh{font-family:inherit;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;border-top:1px solid #ccc;padding:10px 0px 10px 0px;background-color:#fff;}.css-1jz6h6z{font-family:inherit;font-weight:bold;font-size:1rem;line-height:1.5rem;text-align:left;}.css-1t412wb{box-sizing:border-box;margin:8px 15px 0px 15px;cursor:pointer;}.css-hhzar2{-webkit-transition:-webkit-transform ease 0.5s;-webkit-transition:transform ease 0.5s;transition:transform ease 0.5s;}.css-t54hv4{-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-1r2j9qz{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-e1ipqs{font-size:1rem;line-height:1.5rem;padding:0px 30px 0px 0px;}.css-e1ipqs a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;}.css-e1ipqs a:hover{-webkit-text-decoration:none;text-decoration:none;}.css-1o76pdf{visibility:show;height:100%;padding-bottom:20px;}.css-1sw9s96{visibility:hidden;height:0px;}.css-1in8jot{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;font-family:’nyt-franklin’,arial,helvetica,sans-serif;text-align:left;}@media (min-width:740px){.css-1in8jot{padding:20px;width:100%;}}.css-1in8jot:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-1in8jot{border:none;padding:10px 0 0;border-top:2px solid #121212;}What to Know About Covid-19 Booster ShotsThe F.D.A. authorized booster shots for a select group of people who received their second doses of the Pfizer-BioNTech vaccine at least six months ago. That group includes: Pfizer recipients who are 65 or older or who live in long-term care facilities; adults who are at high risk of severe Covid-19 because of an underlying medical condition; health care workers and others whose jobs put them at risk. People with weakened immune systems are eligible for a third dose of either Pfizer or Moderna four weeks after the second shot.Regulators have not authorized booster shots for recipients of the Moderna and Johnson & Johnson vaccines yet, but an F.D.A. panel is scheduled to meet to weigh booster shots for adult recipients of the Moderna and Johnson & Johnson vaccines.The C.D.C. has said the conditions that qualify a person for a booster shot include: hypertension and heart disease; diabetes or obesity; cancer or blood disorders; weakened immune system; chronic lung, kidney or liver disease; dementia and certain disabilities. Pregnant women and current and former smokers are also eligible.The F.D.A. authorized boosters for workers whose jobs put them at high risk of exposure to potentially infectious people. The C.D.C. says that group includes: emergency medical workers; education workers; food and agriculture workers; manufacturing workers; corrections workers; U.S. Postal Service workers; public transit workers; grocery store workers.It is not recommended. For now, Pfizer vaccine recipients are advised to get a Pfizer booster shot, and Moderna and Johnson & Johnson recipients should wait until booster doses from those manufacturers are approved.Yes. The C.D.C. says the Covid vaccine may be administered without regard to the timing of other vaccines, and many pharmacy sites are allowing people to schedule a flu shot at the same time as a booster dose.When Johnson & Johnson’s vaccine was authorized in February, it had several advantages over the other two. As a single shot, it was more convenient than the two-dose formulation from Moderna and Pfizer-BioNTech. It also didn’t have to be frozen to stay viable. But it also provided less robust protection.A clinical trial showed that one dose of J. &. J. had an efficacy rate of 66 percent against moderate to severe Covid-19 worldwide, and 74 percent in the United States. Its efficacy against either severe or critical disease was stronger, at 85 percent worldwide.In its application for a booster, Johnson & Johnson included the results of another large-scale trial that began in November, in which they gave half their volunteers a second dose two months after the first. The other half received a placebo.In August, the company announced that in the portion of the trial that took place in the United States, the efficacy rose to 94 percent. But in its report, the F.D.A. focused on the worldwide results, in which the increase more modest, rising to 75 percent.Against severe to critical Covid-19, two shots had an efficacy of 100 percent. But regulators warned in the analysis posted Wednesday that there was little data from that trial on the Delta variant, which now causes the vast majority of infections in the United States.“The small number of accrued cases confirmed to be caused by the Delta variant precludes any conclusion regarding efficacy against that variant,” they wrote.