Table 2.

Comparison of immunogenicity, contraindication and adverse effects between JYNNEOS and ACAM2000 vaccines.

Characteristics	JYNNEOS Vaccine	ACAM2000 Vaccine
Immunogenicity/duration of immunity	Two weeks after the second dose of JYNNEOS [20]	Four weeks after the single dose of ACAM2000 [17]
Neutralizing antibodies	At day 14, the mean titer of neutralizing antibodies was 16.2 [19]. At week 6, the mean titer of neutralizing antibodies was 153.5 [19]	At day 14, the mean titer of neutralizing antibodies by ACAM2000 was 16.2 [19]. At week 4, the mean titer of neutralizing antibodies was 79.3 [19]
Risks in pregnancy, infancy and in children	JYNNEOS may be administered during pregnancy, breastfeeding and infancy [8]. This vaccine is off-label for children and pregnant women [15,20]	ACAM2000 has a risk of adverse effects and is contraindicated during pregnancy, breastfeeding and in infants [8,17]
Contraindication	For the emergency uses of JYNNEOS, no contraindications are identified. It is contraindicated for people with a history of atopic dermatitis, an allergy to one of the vaccine components. JYNNEOS is safe in persons with immunocompromising conditions [8,16,20]	Pregnancy, breastfeeding, smoking, hypertension, diabetes mellitus, coronary artery disease, cardiomyopathy, people with allergic reactions and anaphylaxis. ACAM2000 is contraindicated in people with immunosuppression conditions, e.g., “leukaemia, lymphoma, human immunodeficiency virus infection, and acquired immune deficiency syndrome (AIDS)” [16,17].
Common adverse effects	Local: pain, redness, swelling, itching, hyperpigmentation, skin discoloration Systemic: fatigue, headache, myalgias, nausea, chills, fever [15,20]	Local: pain, redness, swelling and itching at the site of injection. Systemic: fatigue, fever, muscle pain, headache, lymph node enlargement, malaise, arm soreness, body aches, skin rash, nausea, vomiting, diarrhea, swelling of the face, dizziness and shortness of breath [16,17]
Severe adverse effects	No risk of severe adverse effects such as myopericarditis or cardiomyopathy in recipients of JYNNEOS [15,20]	Increased risk of myopericarditis and cardiomyopathy [16,17]