City of Hope announced that a novel COVID-19 vaccine candidate, COH04S1, may also promote a robust immune response against the mpox virus. Researchers at the institution developed a fully synthetic platform of the highly attenuated modified vaccinia Ankara vector—which was similar to what was used to create the JYNNEOS vaccine. They then used a virtually identical replica of the modified vaccinia Ankara to establish a multiantigen COVID-19 vaccine. Compared with the JYNNEOS vaccine, the COH04S1 vaccine offered a comparable cross-reactive antibody response in human and nonhuman primate models. In a mouse model, the researchers further discovered that when injected with the COH04S1 vaccine or the modified vaccinia Ankara, mice experienced protective effects against the mpox virus strain responsible for the 2022 to 2023 mpox outbreak. The COH04S1 vaccine is currently being evaluated in phase II trials. The researchers hope that if proven effective, the novel vaccine can serve as an alternative to the JYNNEOS vaccine in times of vaccine shortages; may be utilized as a dual vaccine to help simultaneously prevent COVID-19 and mpox infections; as well as protect against other poxvirus strains with pandemic potential that may arise in the future.