Three vaccination sites, one in Colorado and two in North Carolina, briefly paused administering the Johnson & Johnson vaccine against COVID-19 earlier this week after a small percentage of recipients experienced adverse reactions. The shots resumed after investigations by the US Centers for Disease Control and Prevention found the incidents were consistent with the vaccines known side effects.

On Wednesday afternoon (April 7), a mass vaccination clinic at a baseball stadium outside of Denver shut down after 11 people felt unwell within 15 minutes, according to The Denver Post. Their reactions included nausea, dizziness, and fainting; nine people were treated at the site with juice and water, while two were taken to the hospital. More than 1,700 people were vaccinated at the site that day.

After reviewing each patients symptoms, analyzing other vaccinations from the same lot of the vaccine and speaking with the CDC to confirm our findings, we are confident in saying that there is no reason for concern, said Eric France, the chief medical officer of the Colorado Department of Public Health & Environment, in a statement released the following day. We are committed to making sure every community clinic is well-staffed with medical professionals who take patient safety with the utmost seriousness, just as they did at yesterdays clinic.

Yesterday, a similar incident occurred at a mass vaccination site at a sports arena in Raleigh, North Carolina, that had administered more than 2,300 Johnson & Johnson shots. There, 18 people experienced reactions, four of whom were taken to hospitals. The Wake County Public Health department released a statement later that day saying that it had investigated the incident together with the CDC and that the federal agency recommended moving ahead with the vaccines.

We have been administering J&J vaccine here in Wake County since early March, and nationally, more than 4.5 million people have received the J&J shots, Wake County Medical Director Kim McDonald says in the statement. Reactions are expected, but whats important is that our patients are here with us being monitored, and medical personnel are right here in our clinics to respond to these rare events.

There is no greater priority than the safety and well-being of the people we serve. When we receive reports of adverse events in individuals receiving our medicines and vaccines, we collect necessary information and carefully assess the events, Johnson & Johnson spokesperson Lisa Cannellos writes in an email to The News & Observerin Raleigh.

David Wohl, a University of North Carolina School of Medicine infectious disease physician who helps run another clinic that also paused Johnson & Johnson injections yesterday, tells the News & Observer that more people at that site report feeling lightheaded and faint with that vaccine than with the other COVID-19 vaccines the clinic administers. He suggests that may be because people who dread vaccines are seeking out the single-dose Johnson & Johnson version. Were having a lot of people who are taking the J&J vaccine because they dont want two shots because they dont like needles, he says.

Feeling anxious or faint can be common when receiving a vaccination or any kind of medical procedure, like a blood draw, says state epidemiologist Rachel Herlihy in the Colorado health departments statement. When you go to your vaccine appointment, bring a beverage and a snack or a friend or family member to help offer some reassurance.