Vaccines are offered to people at higher risk of the disease, but vaccine doses are limited.
Why it matters
Vaccination could be an important step in curbing the spread of monkeypox, which has been declared a public health condition by the WHO.
What does this mean for you?
Some men who have sex with men are eligible for the vaccine, as are other people who may have been exposed to monkeypox. Due to the limited supply, you will probably only receive the first dose of the two-dose vaccine for now.
The monkeypox epidemic is growing in the US, with most states reporting cases. More than 4,900 cases have been reported nationally, with the most in New York, followed by California. New York state and San Francisco declared local health emergencies on Thursday, moves to open up more funding and expand testing and vaccine resources.
There is a monkeypox vaccine, Jynneos, but access for those who need it has been difficult (some gay and bisexual men are eligible, as are health workers). Federal officials have acknowledged that demand for the vaccine is outstripping supply, and the U.S. Department of Health and Human Services is moving additional doses to states. As of this week, HHS said it had delivered more than 336,000 doses across the US. The government has promised a total of 6.9 million doses will be available by mid-2023, but some critics have warned that the public health response to monkeypox is too slow.
“We’re kind of catching up,” said Dr. Amesh Adalja, an infectious disease expert and chief scientist at the Johns Hopkins Center for Health Security.
In some areas, such as San Francisco, New York City, and Washington, DC, people who are eligible for the vaccine receive only the first dose of a two-dose series. Officials say it will still offer protection against monkeypox and that it is in line with the response in other countries, including Canada and the UK.
Here’s what we know about the Jynneos monkeypox vaccine currently being distributed and who is eligible. Here’s also what you should know about ACAM2000, an older generation vaccine that works against monkeypox.
What is the monkeypox vaccine?
The US has two vaccines in its national stockpile that work against monkeypox. Both are expected to act before exposure to monkeypox and after exposure before symptoms develop. (The fact that vaccines work after exposure distinguishes monkeypox from diseases like COVID-19.)
Jyneos (manufactured by Bavarian Nordic) is a new generation vaccine approved by the US Food and Drug Administration in 2019 against monkeypox and smallpox. It is a two-dose vaccine, with each dose given four weeks apart. It uses a weakened virus and is approved for adults age 18 and older who are at high risk of getting monkeypox or chickenpox.
Jynneos is a vaccine that is being shipped and is currently being used in response to monkeypox in the US. Its supply is limited, but the CDC says more may become available in the coming weeks and months.
Jynneos is the newest monkeypox vaccine, but it’s not the only one in the US stockpile.
ACAM2000 is a second-generation smallpox vaccine that also works against monkeypox. (The two diseases are closely related, and both are caused by orthopoxviruses, which makes it possible.) If necessary, the US Department of Health and Human Services said it is also ready to ship the ACAM2000 vaccine, which is more abundant than Jynneos but remains the second choice in response to monkeypox because it has a side effect profile that is unsafe for some people.
ACAM2000 is given differently than the typical vaccine we are used to. It is administered by dipping a needle into the vaccine solution, which is then “pricked” several times into the upper arm. It causes a localized infection (“distemper”) that triggers an immune response.
While ACAM2000 does not cause smallpox, it does contain live vaccine virus, which is not suitable for everyone. It could be dangerous for immunocompromised people, pregnant people and people with certain heart or skin conditions such as eczema.
Smallpox was declared eradicated from the world in 1980. The US stopped routine vaccination against it in 1972, although some health care workers or people who work in laboratories may have had the vaccine. According to the CDC, ACAM2000 is a derivative of Dryvax, which helped eradicate smallpox.
Who needs the monkeypox vaccine?
The exact criteria for who should get the monkeypox vaccine depends on the city or state people live in and how widespread the outbreak is, but men who have sex with men and who have had multiple or anonymous sexual partners in the past two weeks (met their recent partner or partners through a social media app such as Grindr) are eligible in cities such as New York. That’s because most cases in the current epidemic are in gay and bisexual men, even though anyone in close contact with monkeypox can get sick.
According to the CDC, you meet the criteria for the monkeypox vaccine if you:
- You are in contact with someone who has monkeypox or have been identified as possibly exposed through contact tracing.
- Within the last two weeks, you have had a sexual partner who has monkeypox.
- During the past two weeks, you have had multiple sexual partners in an area with a high incidence of monkeypox.
If you are concerned about monkeypox and think you may be at high risk of exposure, check the current guidelines for your city and state. You can also consult your doctor or book your vaccine appointment online, a process that will guide you through the eligibility criteria. Here is the New York City website for vaccine appointments. You can make an appointment and find the vaccine in San Francisco by calling or visiting one of the city’s clinics.
How effective are vaccines? How long do they take to work?
The CDC says that the Jynneos vaccine takes two weeks (14 days) after the second dose to develop immunity, and that ACAM2000 takes four weeks for maximum immunity. Although many people only receive the first dose of Jynneos at this time, early research suggests that one dose will still offer some protection, at least for a shorter period of time.
Because the monkeypox outbreak in the U.S. is so new, there is no data yet on exactly how effective the vaccines will be in the current situation, according to the CDC. Jynneos’ effectiveness against monkeypox is supported by animal studies, the agency says. And while it won’t be used in most cases, ACAM2000 is closely related to Dryvax, the vaccine that helped get rid of smallpox. The efficacy of ACAM2000 is supported by both animal studies and human clinical trials.
You should still isolate yourself if you develop monkeypox symptoms, such as a rash, after being vaccinated, the CDC says. To be most effective, the post-exposure vaccine should be given within four days of exposure, according to the CDC. If given between four and 14 days after exposure, it may not prevent infection but is expected to reduce symptoms of the disease, the agency says.
Why does the US stockpile monkeypox vaccines?
The US has stockpiles of Jynneos and ACAM2000 on hand, not because the country fears 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 occurred in the 1949s. But smallpox is usually much more serious than monkeypox, and officials fear it could be used as biological warfare.
“The stockpile was created in case of a smallpox biological weapons attack on the United States,” Adalja says. In this case, according to Adalja, health officials would not administer vaccines or use only the newer generation vaccine.
“If there was an attack of smallpox, we would use any vaccines to deal with it,” he added.
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 care provider with any questions regarding health conditions or health goals.