The agencies said they were investigating clots in six women that occurred in the days after vaccination. The clots were observed along with reduced platelet counts - making the usual treatment for blood clots, the blood thinner heparin, potentially "dangerous."
"More investigation has to be done," said UNC Infectious Diseases Dr. David Wohl. "We don't know about underlying conditions. We don't know about other medications. So I think we can't jump to conclusions just yet. But even if these six cases or additional cases emerge of this particular clotting problem, in the context of the benefits of the vaccine, you really have to keep messaging that it's important for people to get vaccinated."
Cape Fear Valley Health announced on Tuesday it is cancelling this week's two scheduled walk-in clinics for the Johnson & Johnson vaccine. The health system's other vaccine clinics, which offer the Pfizer and the Moderna vaccines, remain open and are taking appointments.
UNC-Chapel Hill also announced the Carolina Student Vaccination Clinic will pause its operations on Tuesday.
"Complications from the Johnson and Johnson vaccine are extremely rare," a statement said. "Any student who has already received the vaccine and develops a severe headache, abdominal pain, leg pain, or shortness of breath within three weeks after vaccination should contact Campus Health or another healthcare provider."
Duke Health said it has immediately paused use of the J&J vaccine at all of its sites.
At those sites, patients who were scheduled to receive the J&J are being offered the Moderna and Pfizer vaccines.
Fayetteville State University said there will be no vaccine clinic on campus until further notice due to the pause.
The NCCU COVID-19 Vaccine Clinic said it will suspend use of the Johnson & Johnson vaccine immediately until further notice. The clinic scheduled for Wednesday will now administer the Moderna vaccine, NCCU said. Individuals with appointments already scheduled will be contacted directly.
"I feel like they've done a really good job of monitoring the adverse affects through the CDC monitoring line that they have and until they tell us different, I feel confident knowing a little bit about the virology of the vaccines that we're doing the right thing by continuing to get them into people," NCCU vaccine coordinator Dr. Kristin Long-Witter said.
The Durham County Department of Public Health and Wake County Public Health are also pausing administration of the vaccine.
The Durham health department said all individuals scheduled for vaccine appointments should plan to arrive at their scheduled time and will be offered a Moderna or Pfizer vaccine.
Wake County said its clinics will all shift to Moderna doses.
NCDHHS said it has paused administration of the Johnson & Johnson COVID-19 vaccine until more information is released. "The safety system in place is working as it should," a statement from NCDHHS said. "If you have an appointment for Pfizer or Moderna, please go to your appointment as planned. If you have an appointment for Johnson & Johnson, your appointment will be re-scheduled."
A Walgreens corporate spokesperson told ABC News the chain is pausing use of Johnson & Johnson vaccine "immediately."
UNC Health said it will follow the FDA's recommendation and pause vaccinations using the J&J vaccine "until federal authorities are able to review data and provide further guidance."
CVS issued a statement that said: "We are immediately implementing a pause in the use of the Johnson and Johnson's COVID-19 vaccine per the recommendation from federal health agencies."
More than 6.8 million doses of the J&J vaccine have been administered in the U.S., the vast majority with no or mild side effects.
Johnson & Johnson issued a statement Tuesday that said, in part:
We are aware of an extremely rare disorder involving people with blood clots in combination with low platelets in a small number of individuals who have received our COVID-19 vaccine. The United States Centers for Disease Control (CDC) and Food and Drug Administration (FDA) are reviewing data involving six reported U.S. cases out of more than 6.8 million doses administered. Out of an abundance of caution, the CDC and FDA have recommended a pause in the use of our vaccine.
"The benefits of these vaccines really do clearly outweigh risks," Wohl said.
Last week, some North Carolina providers paused J&J vaccinations after some people reported "adverse reactions" to the vaccine.
Similar incidents were reported in Colorado and Georgia.
All reactions occurred during the 15-minute observation period after receiving any COVID-19 vaccine.
The CDC issued a statement last week that said an "analysis by the CDC did not find any safety issues or reason for concern" and the agency recommended that providers continue to administer the vaccine.
In Colorado, COVID-19 Incident Commander Scott Bookman said, despite the hospital transport, the side effects the patients reported were "consistent with what can be expected" from the Johnson & Johnson vaccine.
"We know it can be alarming to hear about people getting transported to the hospital, and we want to assure Coloradoans that the CDC and public health are closely monitoring all the authorized vaccines continually," Bookman said. "Based on everything we know, it remains true that the best vaccine to get is the one you can get the soonest."
At the time, Johnson & Johnson sent the following statement to ABC News:
"There is no greater priority than the safety and well-being of the people we serve, and we carefully review reports of adverse events in individuals receiving our medicines and vaccines. Any report about individuals receiving our COVID-19 vaccine and our assessment of that report is shared with the U.S. Food and Drug Administration and other appropriate health authorities. This is part of the established process to inform health authorities' comprehensive surveillance programs that monitor the overall safety of medicines, as well the vaccines authorized for use against this pandemic. We are collecting the necessary information, including from the local vaccination center, to assess these reports."