Mass vaccination sites in five different states reported clusters of people stricken with anxiety and fainting after receiving the Janssen COVID-19 vaccine April 7-9, 2021, the Centers for Disease Control and Prevention (CDC) reports.1

The reactions appear to be psychological, since nothing was wrong with the lots of vaccine, and all of the people examined had no clinical medical problems. The incidents occurred before the national pause on Janssen immunization as a result of rare blood clot reactions. Immunization with the vaccine has resumed, and the pause is over.

However, women younger than age 50 years should be aware that they are at risk of the rare but real side effect of blood clots.

Overall, 15 women have had the reaction and three have died, the CDC reports. The reaction has not been observed with the other two vaccines approved for use in the United States, and the Pfizer and Moderna vaccines have continued to be administered.

The lead CDC investigator of the anxiety reaction clusters hypothesizes that those with an acute fear of needles sought out the Janssen vaccine, since it is a one-dose shot that requires no second vaccination. It is possible that a chain reaction of hysteria occurred in some people, after seeing other vaccinees faint. Overall, among 8,624 Janssen COVID-19 vaccine recipients, 64 people had the anxiety reactions.

The most commonly reported signs and symptoms were light-headedness or dizziness (56%), pallor or excessive sweating (31%), fainting (27%), nausea or vomiting (25%), and hypotension (16%).

The CDC interviewed vaccination site staff members to gather additional information about the reported events and vaccination site practices. Four of the five sites closed temporarily while an investigation took place.

“Thirteen (20%) of the affected patients informed staff members of a history of fainting associated with receiving injections or needle aversion,” the CDC reported. “Among the 64 total cases, 39 (61%) occurred in women. Median patient age was 36 years (range 18-77 years). Most events resolved within 15 minutes with supportive care. Thirteen (20%) patients were transported to an emergency department for further medical evaluation. Among these, five for whom follow-up information was available were released from medical care on the same day.”

Hospital Infection Control and Prevention (HIC) spoke to the lead author of the report, Allison Hause, PhD, an epidemiologist in the CDC immunization branch. The following interview has been edited for length and content.

HIC: Just to reiterate, these clusters occurred before the Janssen vaccine was paused. Have there been any more reports since the resumption of vaccinations?

Hause: These clusters of anxiety-related events were reported to CDC before Janssen COVID-19 vaccine was paused. No additional reports have been reported to CDC.

HIC: The fact that these were in clusters suggests that these patients could have triggered others to have the same reaction. Can you comment on this theory or why you think they would occur in clusters rather than random individual cases?

Hause: At some sites, some events did occur within a close window of time. A person who witnesses an adverse event may become nervous and experience an anxiety-related event themselves, especially if that person is needle-phobic. When this occurs at mass vaccination sites, it can cause a chain reaction.

HIC: Have these reactions been seen to this degree with the other two approved vaccines in the United States?

Hause: We have not received reports of similar clusters following the mRNA COVID-19 vaccines.

HIC: At this point, are these considered primarily psychological (fear) reactions or is there any concern that the vaccine could cause this side effect? Were the lots involved in these clusters inspected?

Hause: The events described in this report are consistent with the definition of anxiety-related events following vaccination. It’s possible that individuals with a fear of needles have sought out the Janssen COVID-19 vaccine because it is a single dose. We do not consider these events to be a safety concern associated with Janssen COVID-19 vaccine. We performed a vaccine lot analysis for the vaccine used at each site to determine if a particular vaccine lot was associated with these events. No safety issues or clustering of adverse events indicated a product quality problem.

HIC: Was this phenomenon reported in the clinical trials?

Hause: In the Phase III trial, syncope [fainting] was reported for one person (of 21,895) who received Janssen COVID-19 vaccine. Of the 21,888 persons who received placebo, none experienced syncope.


  1. Hause AM, Gee J, Johnson T, et al. Anxiety-related adverse event clusters after Janssen COVID-19 vaccination — Five U.S. mass vaccination sites, April 2021. MMWR Morb Mortal Wkly Rep 2021;70:685-688.