Mpox Vaccine Effectiveness Evaluation

In August 2022, mpox (formerly called monkeypox) was declared a Public Health Emergency in the United States due to rapid and ongoing transmission. The outbreak disproportionately affected gay, bisexual, and other men who have sex with men, as well as transgender and nonbinary people. To curb the spread of mpox, the FDA issued an emergency use authorization (EUA) for a 2-dose vaccine series designed to protect against mpox and smallpox. Though the incidence of mpox has substantially declined, transmission is still occurring, and the risk of renewed outbreak remains a public health concern. Since October 2022, the Yale EIP has collaborated with the CT Department of Public Health, the CDC, and EIP sites in other states to conduct a case-control study for evaluating effectiveness of mpox vaccines. The purpose of the project is to provide real world evidence of vaccine effectiveness which will inform vaccination recommendations and can be used to promote higher vaccine uptake in populations at risk.

• Estimate vaccine effectiveness of 2-dose JYNNEOS™ vaccine series against mpox disease.
  
• Estimate vaccine effectiveness by number of doses, route of administration, time since vaccination, or other relevant subgroups to assess the duration and variability of protection.
• Use results to inform vaccination recommendations and promote higher uptake of mpox vaccines in high-risk populations.

The Mpox Vaccine Effectiveness Evaluation program conducts statewide monitoring for new diagnoses of mpox disease and invites eligible individuals (case participants) to participate in the project through a brief web-based survey. CT EIP partners with healthcare facilities and community-based organizations across CT that serve the LGBTQ+ community to offer the survey to people without mpox (control participants) for comparison of vaccine effectiveness. The survey is distributed by the CT EIP and asks participants about vaccinations or treatments that may have been received, health status, and potential mpox exposures. The primary objective of the survey is to estimate vaccine effectiveness by number of doses, route of administration, time since vaccination, or other relevant subgroups to assess the duration and variability of protection. Initial results were published in May 2023 and found that 2 doses conferred substantial protection against mpox. This study is ongoing.

Dalton AF, Diallo AO, Chard AN, et al. Estimated Effectiveness of JYNNEOS Vaccine in Preventing Mpox: A Multijurisdictional Case-Control Study — United States, August 19, 2022–March 31, 2023. MMWR Morb Mortal Wkly Rep 2023;72:553–558. DOI.

CDC:

• U.S. Outbreak Cases and Data Dashboard
• Mpox Vaccination Basics
• Mpox Morbidity and Mortality Weekly Reports

CT Department of Public Health:

• Mpox vaccination FAQs, upcoming vaccination events, and clinics offering mpox vaccination

Adeline Morris, MPH

Epidemiologist
Connecticut Emerging Infections Program
One Church Street, 7th Floor
New Haven, CT 06510
(203) 737-3694
vaccineeffectivenesseip@yale.edu

Staff

AmberJean Hansen, MPH