The Johnson & Johnson vaccine was just about to break through.
While it had only recently started to roll out, states, cities and clinics had big plans for it as an important weapon in the fight against Covid-19. The one-shot vaccine could do what the two-shot Pfizer and Moderna vaccines couldn't. It could reach the homeless and even be distributed door to door. It could fill the gaps at a crucial point in vaccination efforts that were already losing momentum.
But on Tuesday morning, the Johnson & Johnson vaccine became the focus of international scrutiny after federal health authorities recommended pausing its use after six women ages 18 to 48 developed a very rare type of blood clot in the brain after they got the shots. A review from the Centers for Disease Control and Prevention and the Food and Drug Administration is expected in the coming days.
And while White House officials have stressed that the Pfizer and Moderna vaccines will help pick up the slack, it's the kind of jarring news that some public health experts worry could deepen suspicions among people who are already skeptical of vaccines and introduce new uncertainties for those who might be on the fence at a precarious time when new cases are surging in many states.
"As it plays out, this is the sort of thing that increases the possibility of vaccine hesitancy across the board," said Dr. Steve Schrantz, an assistant professor of medicine at the University of Chicago, who specializes in infectious diseases. "It's a very hard thing to message, and it can put further doubt in people's minds."
The U.S. had been averaging more than 3 million shots a day since early April, but vaccination numbers in some states that had been on the upswing were leveling off. On Feb. 13, West Virginia was among the country's leaders in vaccinations, having administered 95 percent of doses delivered to it. But the state's efficiency has fallen in recent weeks, and as of Monday it had administered just 74 percent of its doses.
West Virginia is one of several Southern states where vaccine efficiency rates have fallen since the end of February; Alabama, Arkansas, Georgia, Louisiana, Mississippi, Missouri, North Carolina, South Carolina and Tennessee are all administering their vaccine doses more slowly than had been earlier in the year.
And the consequences of halting use of the Johnson & Johnson vaccine were already being felt in many communities.
Local health officials in Worcester, Massachusetts, had expected to receive at least 20,000 doses of the Johnson & Johnson vaccine each week over the next month for use by two community health centers, part of a program to vaccinate Black and Latino residents, who together are about a quarter of the city's population but half of its Covid-19 patients.
"We try to reach the folks who don't usually access health care in the conventional way," said Dr. Michael Hirsh, medical director for Worcester's Public Health Division.
Hirsh said the city hasn't had to cancel any clinics yet — it relied on a supply of Pfizer doses as a replacement at a pop-up clinic Tuesday — but he said he's not sure what comes next.
"I think we have enough to get us through this week," he said. "We have to make sure that Moderna and Pfizer can help us to compensate for this loss."
Bristol Health, a Connecticut health system, had been using the Johnson & Johnson vaccine at a mobile clinic at the nearby headquarters of ESPN, where it administered 500 Johnson & Johnson doses Monday. For now, it plans to switch to Moderna and Pfizer doses for the clinic and for hospital patients being discharged to nursing homes, even though coordinating second shots for such patients can be complicated.
"Now, we have to figure out how we go to the nursing home and plan to give them their second dose," said Albert Peguero, manager of emergency preparedness at Bristol Health.
And in Anchorage, Alaska, the Alaska Native Medical Center had been counting on Johnson & Johnson's one-dose regimen to vaccinate a different hard-to-reach population: Native people who travel for hours, often by air, from rural areas for specialized medical care, such as a surgery.
"What we were looking at doing was helping people get vaccinated while they're in the hospital," said Shirley Young, a spokesperson for the hospital.
Patients will be offered Pfizer or Moderna shots, she said, but scheduling second shots may be difficult. "Time will tell what people choose to do," she said.
Biden administration officials maintained that the Johnson & Johnson pause won't derail the administration's vaccination goals. Jeff Zients, the White House Covid-19 response coordinator, said in a statement that 25 million doses of vaccines made by Pfizer and Moderna have been distributed every week and that 28 million doses will be made available this week. Pfizer announced Tuesday afternoon that it would boost vaccine production to deliver 10 percent more doses than it had previously promised.
"This is more than enough supply to continue the current pace of vaccinations of 3 million shots per day," Zients said, "and meet the President's goal of 200 million shots by his 100th day in office — and continue on to reach every adult who wants to be vaccinated."
More than 6.8 million people in the U.S. have received the Johnson & Johnson vaccine. In the six reported cases involving clots, the patients developed blood clots in the brain known as cerebral venous sinus thrombosis, as well as low levels of blood platelets.
Dr. Sarah Fortune, a professor of immunology and infectious diseases at the Harvard T.H. Chan School of Public Health, said that even if the vaccine is linked to blood clots, the benefits of the shot far outweigh the risk of developing such a side effect.
"These are really low numbers," she said. "Basically 1 in a million. We accept much higher risks than that any time we drive on a highway."
But Tuesday's announcement was by far the biggest hurdle in what had been a historic development and distribution process that had encountered few major issues. Because of public health efforts to reassure people about the safety of the vaccines, hesitancy among some groups had been declining.
Dr. Jorge Moreno, an assistant professor of medicine at Yale School of Medicine, said that rather than induce panic, the pause should demonstrate that federal health authorities are taking safety concerns seriously.
"This should provide reassurance that the regulatory bodies are doing their job," he said. "It shows that the mechanisms in place to catch these rare events are working."
But the pause could become a tool for anti-vaccination activists like Robert F. Kennedy Jr. and others who are distributing misinformation, who leaped on the news as part of their efforts to undermine faith in vaccines in general.
Kolina Koltai, a postdoctoral fellow at the University of Washington who researches vaccine misinformation, said anti-vaccination groups used similar tactics last month when several European countries temporarily halted use of the Oxford-AstraZeneca vaccine over similar blood clot concerns.
"There will be a variety of frames on this pause, including saying this is evidence that this vaccine and therefore all vaccines are unsafe," Koltai said. "They are possibly going to say that the numbers are much higher than six cases. Beyond those classic narratives, people are going to talk about how this is an 'experimental' vaccine and say that it should have never gotten approved or would have never gotten approved during non-pandemic times."
Seizing on real news about vaccine safety is a common misinformation tactic.
"Every unexpected news about vaccines is an opportunity to piggyback medical misinformation into public conversation," said Joan Donovan, research director of the Shorenstein Center on Media, Politics and Public Policy at the Harvard Kennedy School. "This is why we need platform companies to have a plan for the curation of news related to health. Anti-vaccination activists depend on this lack of oversight to exaggerate risks and introduce misinformation into the news cycle."
Vaccination debates also played out in the Facebook comments on local news stories around the country Tuesday. "So much for those of us opposed to getting the vaccine being conspiracy theorist," one person wrote.
But some public health advocates were skeptical about the success of anti-vaccination groups.
"I know lots of folks think this will cause more vaccine hesitancy — and more harm than good," tweeted Dr. Ashish Jha, dean of the Brown University School of Public Health. "I'm honestly not so sure. My sense is confidence comes from people believing that we have a vigorous system that takes adverse events seriously."