Out of the 2,300 Johnson and Johnson vaccines administered on Thursday at the site, Wake County officials said 18 total patients reacted to the vaccine. Four were transported to local hospitals and fourteen others had minor reactions. The four others are being evaluated and are expected to be released.
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All reactions occurred during the 15-minute observation period after receiving any COVID-19 vaccine.
The Johnson & Johnson vaccine is only one shot, in contrast to the two-dose Moderna and Pfizer vaccine.
In place of the Johnson & Johnson vaccine, Wake County went forward with using the Pfizer vaccine on Friday. However, officials said it plans to begin administering the J&J vaccine again soon.
Wake County health officials said the reactions to the vaccinations are "consistent with known common side effects from receiving the vaccine."
The most common side effects are arm soreness, fatigue, body aches and, in some cases, a low-grade fever.
The CDC issued a statement Thursday evening 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.
"We know it can be alarming to hear about or see people having reactions to vaccination - this is why we closely monitor those we vaccinate in case of reaction," said Wake County Public Health's Medical Director Kim McDonald, "Right now we are working with NCDHHS and the CDC to further evaluate the situation to assure everyone is confident in the continued safety of our vaccine operations."
An NCDHHS spokesperson said in a statement: "We are working with the Wake County Public Health team to investigate reactions to the Johnson & Johnson COVID-19 vaccine at an event at the PNC Arena today. Out of an abundance of caution, Wake County Health Department has paused use of the Johnson & Johnson vaccine at this event at this time. We have not had reports of other increased rates of reactions at any other provider, but will continue to investigate. We have notified Johnson & Johnson and are in contact with the Federal Government."
UNC Health initially told ABC11 it would continue to administer J&J vaccines, but then later said it has paused its administration of the vaccines for Thursday "out of an abundance of caution."
"Over the past two days, UNC Health has administered more than 2,200 J&J doses in patients at our largest vaccine clinic, Chapel Hill's Friday Center, and our Hillsborough Hospital clinic. We will work closely with our partners, including Wake County and the State of North Carolina, to share any new information. Our patients' safety and health is our top priority," a statement from a spokesperson said.
In an updated statement on Friday, UNC said it plans to resume J&J vaccinations on Saturday.
"We believe that the J&J vaccine is safe," the statement said. "Very few people (less than 1%) who have received this vaccine at our clinics have reported lightheadedness or fainting."
Duke Health issued the following statement on Friday:
"No patients at Duke have experienced serious incidents. Minor side effects from the vaccine have been consistent with those reported by the manufacturer prior to authorization and remain within expected rates. As a result, we do not plan to pause vaccinations at this time and will continue to follow all vaccination policies and guidance from the CDC."
Operations at a mass vaccination clinic in Denver closed on Wednesday after 11 people who received vaccinations with the Johnson and Johnson dose also had 'adverse reactions,' ABC-affiliate KMGH reports.
The Colorado Department of Public Health and Environment originally said patients experienced symptoms like nausea and dizziness. Nine of the patients were treated on-site with juice and water.
But on Thursday, Colorado Governor Jared Polis said there "weren't any issues" with the vaccines.
"Maybe they were dehydrated or scared of needles," Polis said at a Thursday news conference. Two people were taken to a hospital for observation.
Despite the hospital transport, the side effects the 11 patients reported were "consistent with what can be expected" from the Johnson & Johnson vaccine, COVID-19 Incident Commander Scott Bookman told CNN in a statement.
"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."
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."
"It's relatively common to experience side effects from any of the three vaccines available in the US -- about 10% to 15% of volunteers in vaccine trials developed "quite noticeable side effects," former Operation Warp Speed Chief Scientific Adviser Moncef Slaoui said late last year.
Nausea, like the 11 patients in Colorado experienced, headaches and swelling at the injection site may occur, too, according to the US Centers for Disease Control and Prevention.
Severe side effects, like an allergic reaction, are far less common, occurring around every two to five per million people, Baylor College of Medicine dean Dr. Peter Hotez told CNN earlier this month.
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CNN contributed to this report.