The U.S. Food and Drug Administration and Centers for Disease Control and Prevention released a joint statement earlier in the morning saying they are investigating six cases of potentially dangerous blood clots.
To date, roughly 6.8 million people have received the Johnson & Johnson vaccine nationwide.
"Right now, these adverse events appear to be extremely rare. COVID-19 vaccine safety is a top priority for the federal government, and we take all reports of health problems following COVID-19 vaccination very seriously," their statement read in part. "People who have received the J&J vaccine who develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their health care provider.
The agencies recommended a "pause" while they review the data and evaluate the next steps.
As CBS's Alice Gainer reports, if you had an appointment already scheduled at New York state mass vaccination sites like the Javits Center for the J&J vaccine, don't cancel it. Officials say you'll just get a different vaccine at those sites instead.
According to the White House, of the three vaccines, J&J makes up less than 5% of the shots people are getting.
Officials around the Tri-State Area say so far there are no reports of blood clots here related to the J&J shot.
In New York City, Mayor Bill de Blasio said there have been 234,000 doses administered so far.
"Thank God, no reports at all to date of any blood clots," he said.
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The mayor publicly got the Johnson & Johnson one-dose shot himself, as did Gov. Andrew Cuomo.
"Our Health Commissioner Dave Chokshi received the shot. We believe in the effectiveness of this vaccine, but obviously we take seriously any warning," said de Blasio. "Everyone who was scheduled to come to one of our centers will get a new appointment, obviously with Moderna or Pfizer."
New York State Health Commissioner Howard Zucker said though extremely rare, "People who have received the J&J vaccine who develop severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact their health care provider."
"The best evidence indicates that vaccines work, and this vaccine is almost certainly going to continue to be part of our armamentarium, but we do want to take that pause," Dr. Jay Varma added.
"In New Jersey, we have administered roughly 235,000 doses of the J&J vaccine, with no similar reported adverse effects," said Gov. Phil Murphy.
"We have administered over 100,000 doses of the J&J vaccine here in Connecticut, said Dr. Deidre S. Gifford, acting commissioner of the Connecticut Department of Health.
Still, all three states are taking the recommendation, and keeping the J&J vaccine on ice for now.
"We do have enough Pfizer and we do have enough Moderna vaccination to keep our schedule," Gov. Andrew Cuomo said.
"I only found out when my mom called me and told me about it at like 8:30 this morning," said Upper West Side resident Marin King.
At the Javits Center, Gainer caught up with people originally scheduled for a J&J dose Tuesday. They were given the option of getting the Pfizer vaccine.
"I liked the Johnson and Johnson because it was only once, but with all kind of what's going on with some of the side effects, like, it's better peace of mind to just know that I'm getting the Pfizer one, and I'll just come back in three weeks," King said.
"I really didn't mind. Either or. I trust whatever they recommended in there," said Astoria resident Edd Costa.
Watch Alice Gainer's report --
In Paterson, New Jersey, the mayor says the city was only using J&J the past two weeks.
"We canceled roughly 600-plus today," Mayor Andre Sayegh said. "Last week we administered 1,300 doses of J&J and the week prior roughly 1,000."
As of Wednesday, that will change.
"For the first time in about two weeks we're doing Moderna again," Sayegh said.
A stock of J&J vaccine arrived Monday morning at a popular mom-and-pop pharmacy in Hoboken, New Jersey. Owner Pete Sutaria says that now has to be set aside.
"We had about 100 vaccines scheduled for today," he told CBS2's Jessica Layton. "Unfortunately, we had to change our plan and cancel them for the time being."
They canceled a planned vaccination clinic on Jackson Street and even put a program to deliver the vaccine to homebound seniors on hold.
"Actually, it was very disappointing because the Johnson and Johnson is the easiest thing. As a pharmacy, we can manage storage," Sutaria said. "So it's definitely very convenient for us as a provider."
Providers aren't worried about doses going bad; they can hold up to 30 days.
They're more concerned about patients who won't want to be vaccinated now, especially where hesitancy has been an issue.
"I don't wanna get vaccinated at all. Blood clots in my body? Come on. That's not good," Hoboken resident Shakeema High said.
"The flu shot I get every year ... so that. But this? No," Hoboken resident Debbie Foster said.
"I'm actually looking into getting vaccinated after the birth. As long as it's not Johnson and Johnson, I'm fine," Hoboken resident Natalie Huggins said.
Dr. Shereef Elnahal, of University Hospital in Newark, has helped to lead the campaign to promote trust of the vaccine in New Jersey, especially in communities of color.
"This is a one-shot, one-dose regiment that was pushed to communities that have a harder time accessing health care," he said.
"Does this set you back?" Layton asked.
"I sure hope not. I think we've made a lot of progress, Jessica," Elnahal said. "It may cause a temporary pause in that, but I hope that's not permanent."
All states say they're working to reschedule appointments and provide other vaccines.
CBS2's Jessica Layton contributed to this report.
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