Clusters of anxiety-related medical incidents have occurred during mass vaccination events involving the Johnson & Johnson COVID-19 vaccine, according to the Centers for Disease Control and Prevention.

During the first five weeks of the drug’s rollout in the United States, five vaccination sites reported 64 medical events that were determined to be due to anxiety. These included 17 syncope, or fainting, episodes, reported Anne M. Hause, Ph.D., and colleagues from the CDC COVID-19 Response Team. 

The rate of fainting incidences from 2019 to 2020 recorded by the federal Vaccine Adverse Events Reporting System was 8.2 per 100,000 doses of the J&J vaccine, the investigators wrote in a report released Friday. That’s compared with 0.05 per 100,000 doses recorded after influenza vaccination in the same time period, they added. 

Anxiety-related events can occur after any vaccination, according to the authors. Vaccine providers should be aware of this fact and monitor recipients for at least 15 minutes following a shot, they said. 

Signs of post-vaccination anxiety may include the following: tachycardia (rapid heart rate), hyperventilation (rapid breathing), dyspnea (difficulty breathing), chest pain, paresthesia (numbness or tingling), light-headedness, hypotension (low blood pressure), headache, pallor or syncope, the authors noted.

There also were six cases reported of people receiving diphenhydramine (an antihistamine), or epinephrine, potentially for allergic reactions, following receipt of the J&J shot. These were not counted in the anxiety group. There were no reported cases of severe allergic reaction, or anaphylaxis.

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J&J vaccine adverse events report released  A review of safety monitoring data has found that 97% of reported reactions after Johnson & Johnsons vaccine administration were not serious, mirroring clinical trial results, according to the most recent data released by the Centers of Disease Control and Prevention. By April 21, nearly eight million doses of the vaccine had been administered. Among those vaccinations, 17 thrombotic events with thrombocytopenia (a blood clot-related condition) have been reported, the investigators said.