CDC provides updated monkeypox vaccine safety data


In a recent report, the Centers for Disease Control and Prevention reported that the JYNNEOS vaccine for preventing monkeypox has not caused severe adverse events in patients aged under 18 years.

JYNNEOS (Bavarian Nordic) vaccine safety in pediatric patients at risk of monkeypox has been supported by recent surveillance, according to a report from the Centers for Disease Control and Prevention (CDC).

JYNNEOS is currently the primary vaccine recommended to protect individuals exposed to monkeypox or at high risk of the disease. It was given an Emergency Use Authorization (EUA) for patients aged under 18 years by the US Food and Drug Administration (FDA) on August 9, 2022. 

There have been 987,294 doses of JYNNEOS administered in the United States from May 22, 2022, to October 21, 2022. During this time, the CDC has surveyed the vaccine’s safety through the Vaccine Adverse Event Reporting System (VAERS) and the Vaccine Safety Datalink (VSD). This surveillance has occurred in patients of all ages.

VAERS collected data from health care providers, vaccine manufacturers, and the public, evaluating for adverse events following vaccination. Vaccine administration errors were included, and intradermal administration saw more administration errors than subcutaneous administration.

VAERS reported no severe adverse events in pediatric patients after administration of the JYNNEOS vaccine, and postlicensure and postauthorization surveillance data indicated overall vaccine safety. This data corresponds to prior safety data for JYNNEOS.

Concerns over myocarditis risk after vaccination were also addressed. The myocarditis reporting rate from VAERS is at least 7 times lower than the background myocarditis rate of 21.6 cases per million over 30 days. 

There were 43,253 JYNNEOS doses recorded in the VSD population, and only 2 cases ofmyocarditis were recorded, both in male patients.

In an emergency Investigational New Drug procedure, 10 of 57 patients reported mild adverse events after the first dose and 5 of 24 after the second dose. These included pain, swelling, erythema, and induration.

Syncope was seen in 1 pediatric patient, but no other adverse events were recorded by VAERS. Other reports for this age group included administration errors, where intradermal administration occurred despite subcutaneous administration being recommended for individuals aged under 18 years.

The CDC has stated it will continue to monitor JYNNEOS safety alongside the FDA. Health care providers have been encouraged to report adverse events to VAERS.


Duffy J, Marquez P, Moro P, et al. Safety monitoring of JYNNEOS vaccine during the 2022 mpox outbreak — United States, May 22–October 21, 2022. MMWR Morb Mortal Wkly Rep. 2022;71:1555–1559. doi:10.15585/mmwr.mm7149a4

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