On May 18, 2023, CDC issued in its Morbidity and Mortality Weekly Report (PDF, 0.99MB) (MMWR) the results of two studies highlighting the effectiveness of the JYNNEOS vaccine in preventing mpox disease. Summaries of these studies are below.

Estimated Effectiveness of JYNNEOS Vaccine in Preventing Mpox: A Multijurisdictional Case-Control Study — United States, August 19, 2022 – March 31, 2023

Summary

What is already known about this topic?
Real-world vaccine effectiveness (VE) estimates for JYNNEOS vaccine against monkeypox (mpox) are limited. To date, no VE estimates by route of administration or for immunocompro­mised persons have been published.

What is added by this report?
In this study, adjusted VE was 75% for 1 dose and 86% for 2 doses of JYNNEOS vaccine, indicating substantial protection against mpox, irrespective of route of administration or immunocompromise status.

What are the implications for public health practice?
Persons at high risk for mpox exposure should be vaccinated with the recommended 2-dose JYNNEOS series.

Effectiveness of JYNNEOS Vaccine Against Diagnosed Mpox Infection — New York, 2022

Summary

What is already known about this topic?
The JYNNEOS vaccine was deployed in a national and state vaccination campaign during the 2022 monkeypox (mpox) outbreak. Postexposure prophylaxis and vaccination of persons at highest risk (primarily men who have sex with men) were prioritized. Evidence of vaccine effectiveness (VE) from con­trolled studies has been limited.

What is added by this report?
A comparison of men aged ≥18 years who received a diagnosis of mpox during July 24–October 31 in New York to controls with rectal gonorrhea or primary syphilis, based on systematically collected surveillance data, found adjusted combined 1-dose (received ≥14 days earlier) or 2-dose VE of 75.7%.

What are the implications for public health practice?
These findings support recommended 2-dose JYNNEOS vaccination consistent with CDC and New York State Department of Health guidance.

The CDC Domestic Mpox Response — United States, 2022-2023

The MMWR also includes an overview of the first year of the response to the U.S. mpox outbreak. The article reviews lessons learned to improve response and future readiness, and previews continued mpox response and prevention activities as local viral transmission continues in multiple U.S. jurisdictions.