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Jynneos Side Effects

Generic name: smallpox and monkeypox vaccine

Medically reviewed by Last updated on Feb 26, 2023.

Note: This document contains side effect information about smallpox and monkeypox vaccine. Some dosage forms listed on this page may not apply to the brand name Jynneos.

Applies to smallpox and monkeypox vaccine: suspension.

Serious side effects of Jynneos

Along with its needed effects, smallpox and monkeypox vaccine (the active ingredient contained in Jynneos) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking smallpox and monkeypox vaccine:

More common

  • Chills

Less common

Incidence not known

  • Chest tightness
  • cough
  • difficulty with swallowing
  • dizziness
  • fast heartbeat
  • hives, itching, rash
  • puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
  • trouble breathing
  • unusual tiredness or weakness

Other side effects of Jynneos

Some side effects of smallpox and monkeypox vaccine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common

  • Bleeding, blistering, burning, coldness, discoloration of the skin, feeling of pressure, hives, infection, inflammation, itching, lumps, numbness, pain, rash, redness, scarring, soreness, stinging, swelling, tenderness, tingling, ulceration, or warmth at the injection site
  • headache
  • muscle pain
  • nausea

For Healthcare Professionals

Applies to smallpox and monkeypox vaccine: injectable suspension, subcutaneous suspension.


There were similar proportion of subjects reporting local or systemic reactions of any severity after the second dose, compared to the first dose, except for injection site pain which was more common following dose 1 (79% vs 69%).[Ref]


None of the reported cardiac AESIs causally related to vaccination were considered serious.[Ref]

Common (1% to 10%): Subcutaneous: Cardiac Adverse Events of Special Interest (AESIs - any cardiac signs or symptoms, changes in ECG, or troponin-1 elevations above 2 times the upper limit of normal)[Ref]


Very common (10% or more): Subcutaneous: Nausea (17%); Intradermal: Nausea (23%), change in appetite (20%)[Ref]


Very common (10% or more): Subcutaneous: Pain (85%), redness (60%), swelling (51%), induration (45%), itching (43%); Intradermal: Erythema (99.5%), induration (99.5%), itchiness (89%), pain at injection site (65%), underarm pain (20%), underarm swelling (10%)[Ref]


Very common (10% or more): Subcutaneous: Muscle pain (43%); Intradermal: Muscle aches (30%), joint pain (18%)[Ref]

Nervous system

Very common (10% or more): Subcutaneous: Headache (35%); Intradermal: Headache (41%)[Ref]


Very common (10% or more): Subcutaneous: Fatigue (30%), chills (10%); Intradermal: Tiredness (51%), chills (14%)

Common (1% to 10%): Subcutaneous: Fever[Ref]


1. Product Information. Jynneos (smallpox and monkeypox vaccine). Bavarian Nordic, Inc. 2021.

2. FDA. Food and Drug Admnistration. Jynneos Health Care Provider Fact Sheet (Emergency Use Authorization) 2022.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.