More Than a Million Mpox Vaccine Doses, but Only 23% of At-Risk People Fully Protected

In August 2022, a vial of JYNNEOS vaccine held one dose. By changing how the vaccine was given — into the skin rather than under it — the same vial could provide up to five. That change, authorized by the Food and Drug Administration on August 9, 2022, and adopted nationwide within two weeks, helped the United States give more than a million doses during its mpox outbreak. Yet by the end of January 2023, only an estimated 22.7 percent of the people at risk were fully vaccinated.

The outbreak

From May 2022 through January 31, 2023, the United States reported 30,157 mpox cases and 32 deaths; more than 86,000 cases were reported internationally. Most infections spread through close, intimate — mainly sexual — contact with people who had symptoms. The 7-day daily average stood at more than 400 cases on August 1, 2022, and had fallen to five by January 31, 2023.

JYNNEOS protects: in preliminary studies, unvaccinated people had 7–14 times the incidence of vaccinated people, depending on the number of doses. CDC recommends it for people at increased risk, including people with known or presumed exposure; gay, bisexual and other men who have sex with men, and transgender, nonbinary and gender-diverse people, with multiple recent partners or a newly diagnosed sexually transmitted infection; people who have had sex at a commercial sex venue or large gathering in the past six months; their partners; and people with HIV or other immune suppression facing possible exposure.

A smaller dose, five times the supply

An intradermal dose (0.1 mL) can produce an immune response equivalent to a subcutaneous injection with about one fifth of the vaccine. After the week of August 20, 2022, intradermal injection became the main route: 85.7 percent of second doses were given that way, against 45.9 percent of first doses.

First and second JYNNEOS doses by week and route of administration. Credit: CDC Immunization Data Lake.

Coverage

Nationally, an estimated 36.7 percent of people at risk had one dose and 22.7 percent two. Coverage varied enormously:

Twenty-two jurisdictions had first-dose coverage of 25 percent or less; only D.C. passed 50 percent for two doses. Vaccine was deliberately sent first to places with more cases. The report did not study why coverage differed, but suggests possible reasons for low coverage: less access and awareness, fewer providers, lower confidence and demand, and concern about stigma.

Equity lagged too: about one in eight first-dose recipients was Black, but Black people accounted for about one in three mpox cases.

How coverage was estimated

The at-risk population was estimated as men who have sex with men who are eligible for HIV preexposure prophylaxis, plus men who have sex with men living with HIV, then raised by 25 percent to cover others eligible — so estimates for individual jurisdictions may be biased. Residence was missing for 8 percent of vaccinations, some jurisdictions do not report sex or race, and vaccination records do not capture sexual orientation or gender identity.

What comes next

Cases fell sharply, but much is unknown about the risk of the virus returning. The report urges finishing second doses for the partially vaccinated, since full vaccination protects better, and targeted outreach to the groups most affected.

Sources

Based on "JYNNEOS Vaccination Coverage Among Persons at Risk for Mpox — United States, May 22, 2022–January 31, 2023," by Lauren E. Owens and colleagues, CDC Mpox Emergency Response Team, Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention; a work of the United States government in the public domain. Data: CDC Immunization Data Lake and AtlasPlus.