New York State Department of Health Leads with Groundbreaking Mpox Vaccine Effectiveness Studies

Findings Support the Approved Use of JYNNEOS as a Two-Dose Series for Mpox Prevention

View the DOH Led Study Here and the CDC Study Here

ALBANY, N.Y. (May 18, 2023) – The New York State Department of Health has published a groundbreaking study on mpox effectiveness in the CDC's Morbidity and Mortality Weekly Report (MMWR). The study, "Effectiveness of JYNNEOS Vaccine Against Diagnosed Mpox Infection: New York State, 2022," looks at the effectiveness of the two-dose JYNNEOS vaccine, following the mpox outbreak in the spring and summer of 2022 that infected individuals throughout the world, including in New York City and across New York State. The Department also contributed to a CDC led publication, "Estimated Effectiveness of JYNNEOS Vaccine in Preventing Mpox Disease Among Adults: A Multijurisdictional Case-Control Study," further supporting overall mpox vaccine effectiveness research. The findings in these studies support the Department's ongoing guidance that two doses of JYNNEOS offers maximum protection against mpox.

"The results of these studies are further evidence that vaccines work as a core layer of protection against mpox infection," Acting State Health Commissioner Dr. James McDonald said. "The scientific innovation demonstrated by this Department's team of researchers affirms that New York remains at the forefront of groundbreaking, evidence-based results. We are pleased to have worked with the CDC to highlight the importance of the JYNNEOS vaccine series and will continue to collaborate with our federal, state, and local partners to ensure we are doing everything to protect New Yorkers and prevent a resurgence of mpox in this state."

Last summer, as COVID-19 cases declined, yet another outbreak arose of uncertain characteristics and proportions. Mpox had been an extremely rare disease, sexual transmission was virtually unheard of, and the public health community had few biomedical tools with which to fight it. One of those tools was the JYNNEOS vaccine, an approved and licensed vaccine that had not been studied in a real-world setting of human-to-human spread, such as last summer's international outbreak. Using state-of-the-art methods and analytical tools, New York State was able to evaluate the effectiveness of the vaccine in near real-time as it was implemented, adding important data to inform future efforts at preventing mpox outbreaks. Preliminary results of this study were presented at February's Advisory Committee on Immunization Practices (ACIP) meeting, setting in motion the current mpox vaccine recommendations for outbreaks.

The case-control study estimated the JYNNEOS vaccine effectiveness against mpox in New York residents (outside of New York City) using data from systematic surveillance reporting. Researchers found that, while receiving one dose of the vaccine offered some protection (68.1%), getting the second dose had even higher protection (88.5%). The findings support the approved use of JYNNEOS as a two-dose series for mpox prevention amid ongoing sexually related transmission of mpox and incorporating JYNNEOS into a broader program of sexual health services.

"One of public health's main roles is creating a scientific base of evidence to drive messaging, programming, and research," Deputy Commissioner for Public Health Dr. Ursula Bauer said. "During public health emergencies, like the mpox outbreak, we often must take action –in this case the vaccine campaign— based on incomplete evidence. We have a responsibility to then study our interventions and determine the effectiveness of our actions. This process is not over and New York State remains committed to seeking answers to these important public health science questions now and in the future."

Despite the current low number of cases and an increase in access to the JYNNEOS vaccine, mpox is still circulating and the return of mpox to communities in New York and beyond remains a very real possibility. In Chicago, health officials have reported a slight uptick in mpox cases, including among individuals who were previously vaccinated, raising concerns over the possibility of renewed summer spread. The CDC has provided updated information on mpox infections after vaccination following the reporting of this cluster. The results published today document the strong protective value of JYNNEOS during the initial 2022 outbreak.

Important steps New Yorkers can take to support their sexual health and protect themselves from mpox include the following:

  • Get vaccinated for mpox.
  • Talk with sexual partners about whether they have a rash or other symptoms consistent with mpox or other SITs, and if so, seek testing and treatment.
  • Avoid skin-to-skin contact with someone who has a rash or other mpox-related symptoms.
  • Anyone exposed to mpox, or experiences symptoms should reach out to a health care provider.

As a part of New York's continued, proactive mpox prevention outreach, the Department launched a robust media campaign to encourage New Yorkers to start or complete their two-dose series of JYNNEOS and to engage with providers and community partners on ways they can work together with New York City and the State to prevent a resurgence in cases. The "It Takes Two" campaign reminds individuals that it takes two doses of the vaccine to ensure maximum protection. The "Know the Skin You're In" campaign is a reminder that mpox can spread through close, personal, skin-to-skin contact. The campaign materials include an mpox social media toolkit that includes graphics and captions available for download and use across social media platforms.

Find nearby vaccination sites by visiting the following:

Learn more about mpox at Mpox ( and at Mpox (Monkeypox) - NYC Health.

Health care providers can find more information at the State Department of Health's Provider Information page, which includes the latest guidance for clinicians on mpox treatment.

The CDC is also offering mpox resources for spring and summer events here and information on mpox vaccine coverage by jurisdiction here.