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The monkeypox vaccine is available to people at higher risk of getting the disease. To stretch out limited vaccine supply, you might be given the vaccine in a slightly different way.
Why it matters
Vaccination is an important tool to slow the monkeypox outbreak happening in the US and other countries. Access to vaccines is crucial for people most at risk.
Some men who have sex with men are eligible for the vaccine, as are other people who may've been exposed to monkeypox.
Jynneos, the monkeypox vaccine, hadn't been put to the real-world test until the current outbreak. So findings released Friday by the US Centers for Disease Control and Prevention are especially promising, showing vaccine effectiveness. Adult men under 50 who were eligible for a vaccine but didn't get one were 14 times more likely to get the disease than people who did get the first vaccine dose, according to the findings.
Though there are still some unknowns about the vaccine, including how long immunity lasts, health officials attribute the slowed growth of the outbreak in the US to increased vaccine access and rates as well as to temporary changes people at higher risk of monkeypox have made to their sexual or social practices.
Recently, the CDC slightly expanded its recommendation for who may get a monkeypox vaccine -- criteria that's more in-line with the eligibility standards set up at the city or local level. At a press briefing in late September, health officials said people can now opt to get the vaccine on their upper back or near their shoulder, if stigma from the temporary mark left by the new intradermal vaccination method is a concern.
Also called "dose-sparing," intradermal types of injections aren't new to health care. But the change in medical guidance on how the monkeypox vaccine can be administered reflects a shortage of Jynneos that's plagued the vaccine rollout since it began. Health officials have touted a national stockpile of vaccines that work against monkeypox as well as smallpox, but getting them out to states and into the arms of people who need them has been a challenge.
Watch this: Monkeypox Explained: What You Need to Know
Who can get a monkeypox vaccine?
Exact criteria for who should get a monkeypox vaccine depend on the city or state that people live in and how widespread the outbreak is there, but generally speaking, people who were exposed to someone with monkeypox or people who might be exposed in the future may be eligible. Because monkeypox is spreading mostly through sexual contact between men, the CDC's criteria mostly focuses on gay and bisexual men.
Intradermal vaccination is a method that injects the vaccine under a more shallow layer of skin, typically on the inner side of the forearm. This should produce a "noticeable pale elevation of the skin," according to the US Centers for Disease Control and Prevention. Because of this mark, health officials now say people can opt to get the vaccine somewhere on their body besides their forearm.
Most vaccines we get these days go either into the muscle in our arm (intramuscular injection) or into the fatty tissue under our skin (subcutaneous injection). Subcutaneous injection of Jynneos is the only authorized method of vaccination for people younger than 18. If you get the monkeypox vaccine intradermally, you'll still need two doses.
When the FDA authorized the new vaccine method, the agency referenced a study published in 2015 that found that a smallpox vaccine given intradermally gave a similar immune response in people compared to the vaccine given subcutaneously.
Jynneos (made by Bavarian Nordic) is a new-generation vaccine approved by the US Food and Drug Administration in 2019 for monkeypox and smallpox. It's a two-dose vaccine, with each shot given about four weeks apart. It uses a weakened virus and is approved for adults 18 and older who are at high risk of getting monkeypox or smallpox.
Side effects of Jynneos may include typical temporary vaccine side effects, including headache, chills and fatigue. There can also be some pain and swelling around the injection site, which can result in what some are reporting as a temporary swollen lump around the injection site.
ACAM2000 is a second-generation smallpox vaccine that also works against monkeypox. According to the CDC, ACAM2000 is a derivative of Dryvax, which helped eradicate smallpox. (The two diseases are closely related and both caused by orthopoxviruses, which makes this possible.) If necessary, the US Department of Health and Human Services said it's also prepared to ship out the ACAM2000 vaccine, which is in greater supply than Jynneos but remains a second choice in the monkeypox response because it has a side effect profile that isn't safe for certain people.
ACAM2000 is administered differently than the typical vaccine shot we're used to, including intradermal injection. It's given by dipping a needle into a vaccine solution which will then be "pricked" several times on the upper arm. It will cause a localized infection (a "pox"), prompting an immune response.
While ACAM2000 doesn't cause smallpox, it contains live vaccina virus, which isn't suitable for everyone. It could be unsafe for immunocompromised people, pregnant folks and those with certain heart or skin diseases, like eczema.
Because of this, it's possible people born before the early 1970s who got the smallpox vaccine might have some cross-protective immunity against monkeypox, according to the WHO, but there is "little immunity" to younger people living in non-endemic countries because they've had no exposure to a similar virus.
How effective are the vaccines against monkeypox? How long do they take to work?
Administering Jynneos within four days of a monkeypox exposure is the best option for stopping the onset of the disease, according to the CDC. If it's given four to 14 days after an exposure, the CDC says, Jynneos may not prevent monkeypox but will likely reduce the severity of symptoms. A report released by the agency found that adult men ages 18-49 who were eligible for the monkeypox vaccine but didn't get a shot were 14 times more likely to get the disease than people in the same group who got the first dose of vaccine at least two weeks earlier.
The CDC says that the Jynneos vaccine takes two weeks (14 days) after the second dose for immunity to build, and that ACAM2000 takes four weeks for maximum immunity.
You should still self-isolate if you develop symptoms of monkeypox after getting vaccinated, such as a rash.
Why does the US have a stockpile of monkeypox vaccines?
The US has a stockpile of Jynneos and ACAM2000 on hand not because the country was worried about an outbreak of monkeypox (which has been endemic in some African countries for years), but in case smallpox becomes a public threat again. Smallpox was declared eliminated in the 1980s, and the last natural outbreak in the US happened in 1949. But smallpox is usually much more severe than monkeypox, and officials worry it could be used as biological warfare.
"The stockpile was created in the event of a biological weapons attack on the United States with smallpox," Dr. Amesh Adalja, an infectious-disease expert and senior scholar at the Johns Hopkins Center for Health Security said. In this event, health officials would not be rationing vaccines or using only the newer-generation vaccine, according to Adalja.
"If there was a smallpox attack, we would be using whatever vaccines we have to be able to deal with it," he added.
Why was there a monkeypox vaccine supply issue?
At the beginning of the outbreak, Jynneos, the newer vaccine specifically approved to prevent monkeypox, was hard to come by for people who were eligible for the vaccine.
Officials who spoke to The New York Times said the supply issue is partly because the government waited too long to ask Bavarian Nordic, which makes Jynneos, to bottle and fill the vaccine order the US had already purchased.
Another report by the Times alleges that the US national stockpile of monkeypox and smallpox vaccines dwindled because the government never replaced the expired doses and instead put money into technology that would extend their shelf life. Part of the reason for this was that the government created the stockpile not for monkeypox but for smallpox, which is a more contagious and often more serious disease officials fear could be used in biological warfare against the US.
The US Department of Health and Human Services didn't respond to a request for comment on the reports.
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.