(CW44 News At 10 | CNN) -- The US Food and Drug Administration issued an emergency use authorization Tuesday that allows health-care providers to change how the Jynneos monkeypox vaccine is administered, stretching out the supply amid high demand. The vaccine can now be given to high-risk adults intradermally, meaning between the layers of the skin, rather than subcutaneously, or under the skin, as it has been given up till now. This will allow providers to get five doses out of a standard one-dose vial.
The new EUA also allows subcutaneous vaccination in people under 18 who are at high risk of infection.
The move could increase the number of vaccine doses in the national stockpile from 441,000 to over 2.2 million, officials said Tuesday.
But the EUA isn't going to be a panacea as the outbreak continues to grow and vaccine demand remains high. The US Centers for Disease Control and Prevention has estimated that at least 1.5 million people in the US are eligible for the two-dose vaccine.
"I think we're going to see that we will likely still run out of vaccines before we run out of arms," Dr. Demetre Daskalakis, the White House's assistant national response coordinator, said Tuesday.
The CDC reports 9,492 probable or confirmed monkeypox cases in 49 states, Puerto Rico and the District of Columbia as of Tuesday evening.
Moving "as quickly as possible"
"In recent weeks the monkeypox virus has continued to spread at a rate that has made it clear our current vaccine supply will not meet the current demand," FDA Commissioner Dr. Robert Califf said in a statement. "The FDA quickly explored other scientifically appropriate options to facilitate access to the vaccine for all impacted individuals. By increasing the number of available doses, more individuals who want to be vaccinated against monkeypox will now have the opportunity to do so."
He added at a briefing Tuesday, "we encourage jurisdictions to utilize alternative dosing method as quickly as possible, and we'll be your partner in this step every step of the way."
The move comes less than a week after the Biden administration declared monkeypox a public health emergency, which gives the FDA and other government health agencies more flexibility to fight the spread of the virus.
Earlier Tuesday, US Department of Health and Human Services Secretary Xavier Becerra issued a determination to pave the way for the FDA's move.
"Last week, I declared monkeypox to be a public health emergency to unlock additional tools that will help us contain and end this outbreak and to signal to the American people that we are taking our response to the next level," Becerra said in a statement. "Today's action will allow FDA to exercise additional authorities that may increase availability of vaccines to prevent monkeypox while continuing to ensure the vaccine meets high standards for safety, effectiveness and manufacturing quality."
Prevention remains important
The CDC is launching an outreach program to ease the transition to the new strategy, expanding its education and information efforts for public health officials and health care providers. Vaccine equity will be a key part of this message, as will training and outreach on how to use the special needle for intradermal vaccination.
Officials also emphasized that people should continue to take steps to protect themselves from the monkeypox virus even after they're vaccinated, especially those in the hard-hit population of gay and bisexual men and other men who have sex with men. This includes avoiding skin-to-skin contact with someone who may be infected and limiting the number of sex partners.
"Really, prevention for monkey pox is multidomain," Daskalakis said. "And so as people are working to get vaccinated ... we really want to give people options and clear guidance of what to do between the first and second dose and also to be aware that it does take time after the second dose to also achieve adequate protection."
Jynneos is given as two doses at least four weeks apart. Officials said Tuesday that people who have gotten a first dose subcutaneously can get the second intradermally.
Research will continue
Using a smaller dose with intradermal injection has been done with vaccines for flu and rabies, epidemiologist Dr. Jay Varma told CNN in an email. Intradermal shots are also used for the tuberculosis skin test.
"The skin has special cells that are very good at helping a vaccine stimulate the body's immune system," he wrote.
These cells, called dendritic cells, are better able to produce an immune response, said Dr. Daniel Griffin, an infectious disease specialist at Columbia University.
"They live in the skin, and they're better at teaching the immune system what they need to respond to," he said.
A 2015 study found a similar immune response when the vaccine was given intradermally in doses one-fifth the size of those given subcutaneously. Side effects like redness, itchiness and swelling were more common with the intradermal method, but there was less pain.
Jynneos has also been found to be safe and effective in people with conditions that weakened their immune system, Califf said Tuesday.
However, the existing research on the vaccine focuses on recipients' immune response, not on whether it actually prevents cases of monkeypox.
"There is no traditional assessment of this vaccine ... because there weren't smallpox cases, and the monkeypox outbreaks before this were not large enough to really do a clinical trial," Dr. Peter Marks, director of the FDA's Center for Biologics Evaluation and Research, said Tuesday. "We want to collect outcome data, as we do with all vaccines. And I'd also point out that the NIH will be mounting a clinical trial and is working through the logistics of that now."
The move to allow vaccination in children is based on findings around its use in adults, as well as data on pediatric smallpox vaccination, the FDA says.
The agency isn't authorizing intradermal vaccination in kids for two reasons: "First of all, we want to make sure we get it right, and we don't have the data in children that we have in adults," Marks said. "Second of all, as a practicing physician -- I know I'm not a pediatrician; I've treated pediatric patients at times -- we have had to give this vaccine to the youngest of children, and ... giving an intradermal injection to a baby is actually just a little more challenging at times."
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