The U.S. Food and Drug Administration (FDA) granted emergency use authorization (EUA) for JYNNEOS on 9 August 2022, allowing medical professionals to administer the vaccine through intradermal injection to patients who are at high risk for monkeypox infection and who are aged ≥ 18 years. The FDA five-folded the total number of dosages available for usage after receiving the authorization.

The EUA also permits subcutaneous injection of vaccine to be provided to children who are at high risk of monkeypox infection and are aged less than 18 years. In year 2019, this Modified Vaccinia Ankara (MVA) vaccine was authorized by FDA to prevent smallpox and monkeypox. For subcutaneous injections, JYNNEOS is given in 2 dosages under the skin, spaced four weeks apart. A fraction of the vaccine dosage must be administered via intradermal route.

The EUA now permits a portion of JYNNEOS dose to be injected intradermally between the layers of skin for those eighteen years of age and older who are considered to be at elevated risk of contracting monkeypox. It will still be necessary to administer the vaccine twice, four weeks (28 days) apart. The current outbreak of monkeypox cannot be controlled with a single dose of JYNNEOS since there is no evidence that it will offer long-lasting protection.

The results from a clinical study of Jynneos conducted in 2015 support the EUA, which compared the effects of a 2-dose series given intradermally to those given subcutaneously. People who got the vaccine intradermally were administered a lower volume (one-fifth) when compared to people who got the vaccine subcutaneously. The results revealed that the immune responses in the subcutaneous and intradermal intervention arms were comparable. Subjects in both arms were found to similarly respond to vaccination.

The rate of injection site reactions (such as swelling, itching, stiffness, and redness) was greater in those who got intradermal administration, although there was less pain and tolerable side effects. According to the FDA, Jynneos' known and potential advantages outweigh its known and possible hazards when used for approved purposes.

Jynneos subcutaneous use in people under the age of 18 is also supported by safety and immunological response data that are now available in adults, as well as historical information with the utilization of live vaccinia virus smallpox vaccination in pediatrics. In the clinical trials conducted to support approval, JYNNEOS has been examined in patients with immunocompromising diseases and has been determined to be both efficient and safe. In the case of a smallpox outbreak, it was first created primarily as a substitute for usage in immunocompromised people.

For allowing unapproved uses of approved vaccines or emergency usage of unapproved vaccines, FDA may issue a EUA if the public health emergency has the potential to affect national security or the security and health of citizens abroad, and that there are circumstances that support the use of vaccines in an emergency. Hence, authorization of JYNNEOS emergency use would expedite access to the vaccine for all affected people. By raising number of dosages available, more number of people who want to get vaccinated against monkeypox virus would now have the option to do so.