A growing number of states now say they are moving to vaccinate some of their at-risk residents against monkeypox, as the U.S. response accelerates to an outbreak that now spans more than 400 confirmed or suspected cases around the world. 

In the United States, health officials have tallied up to 13 cases so far in eight states: California, Colorado, Florida, Massachusetts, New York, Utah, Virginia and Washington. 

However, only a small handful of Americans will be eligible to receive the shots for now. 

Health officials tell CBS News that doses of the Jynneos monkeypox vaccine are being offered to only at-risk close contacts of monkeypox cases in at least four jurisdictions for now: Colorado, Massachusetts, Virginia and Washington. 

“Vaccine is typically only used if we are concerned about a higher risk type of exposure. Not everyone who is assessed as a contact receives vaccine, because we know that monkeypox is not as easily transmissible as other viruses like COVID-19,” Dr. Julia Murphy, public health veterinarian for the Virginia Department of Health, said in a statement. 

Health officials in Virginia announced a case on Thursday, in an adult woman who did not need to be hospitalized and is now isolating at home. 

“After consultation with the CDC, one person who is a contact of the case is receiving Jynneos,” Murphy said. 

Doses of the vaccine are being shipped out to states from the federal government’s stockpile. A spokesperson for Colorado’s health department, which announced a monkeypox case on Thursday, said they received their shipment by Friday morning.

The rollout serves as an early test for Bavarian Nordic’s Jynneos, which was approved in 2019 by the Food and Drug Administration for smallpox and monkeypox. 

Typically, only select types of laboratory and health care staff who risk exposure through their jobs are vaccinated for orthopoxviruses — the family of viruses that includes both smallpox and monkeypox. 

Jynneos is so new that the CDC only published its formal recommendations for use of the vaccine in the agency’s Morbidity and Mortality Weekly Report on Friday, following a months-long deliberation among its outside vaccine advisers. 

“Today’s MMWR comes at an opportune time, with the current increase in monkeypox cases internationally; however, the new guidelines were not created in response to the monkeypox outbreak,” the CDC said in a statement. 

Previously, the U.S. had only had one vaccine available to head off orthopoxviruses, called ACAM2000. Jynneos has several advantages over ACAM2000, including lower risks of bad side effects and easier administration. 

“CDC experts have been working to refine usage recommendations during the past two years,” the agency’s statement said, adding that the guidance was unanimously approved by its advisory panel late last year.

Supply of the vaccine

It is unclear exactly how many doses of Jynneos will be available for use in the U.S. if the outbreak swells. 

Bavarian Nordic, which credits the U.S. government for pouring millions of dollars into the company’s development of the vaccine, claimed earlier this month to investors that it had “supplied nearly 30 million doses” of a liquid-frozen version of its vaccine for the federal Strategic National Stockpile to date. 

However, the company had acknowledged in 2019 it was in the process of working “to replenish and potentially expand the stockpile, which has expired” with a different “freeze-dried” formulation of the vaccine. 

“Right now, we have over a thousand doses of that available, and we expect that level to ramp up very quickly in the coming weeks as the company provides more doses to us,” the CDC’s Jennifer McQuiston told reporters on Monday. 

McQuiston added later that the Biden administration had over 100 million doses available of ACAM2000, but acknowledged that — given that shot’s downsides — “a decision to use that widely would have to have some serious discussion behind it.” 

A spokesperson for the Department of Health and Human Services — which manages the Strategic National Stockpile — acknowledged “multiple requests” for Jynneos from around the country, but did not offer a specific figure on the country’s expected supply. 

“We stand ready to review and support additional jurisdictions requests, as needed,” the spokesperson said. 

Not all cases identified in the U.S. have been linked to recent international travel to countries now facing active monkeypox outbreaks, CDC Director Dr. Rochelle Walensky told reporters on Thursday. 

“I think that we need to presume that there are some community spread, but there is active contact tracing that is happening right now to understand how these cases might have been in contact with each other or with others in other countries,” said Walensky. 

However, officials said that the discovery of potential community spread in the U.S. was not a cause — for now — to shift the country’s monkeypox vaccination strategy. 

“Right now, while we are in the early phase of investigating this, we know that those at highest risk of infection are those who had contact with a known monkeypox patient with the kind of contact that would facilitate spread,” McQuiston said on Thursday. 

“We continue to watch what is happening, and think about whether wider vaccination recommendations would make sense,” McQuiston added.