“Monkeypox is a zoonotic viral infection that can cause a rash similar to that seen in smallpox. Its clinical manifestations can include fever, chills, swollen lymph nodes, aches and pains. Fortunately, deaths from monkeypox mono are quite rare,” he says. Martin Hirsch, MD, editor-in-chief of infectious diseases for Wolters Kluwer’s UpToDate, senior physician at Massachusetts General Hospital and professor of medicine at Harvard Medical School.
The virus spreads mainly through direct contact with infected skin, sores or bodily fluids, he says, or through indirect contact with objects used by a sick person (such as blankets or clothing). It can also be transmitted through the placenta from an infected person to their fetus.
As a result, the federal government finally announced this week that the virus is a national public health emergency. The declaration opens the allocation of resources and funds to manage the spread of the virus, including the distribution of vaccines.
The good news is that there are two different vaccines for the virus that have been around for years, and allocation of these shots has been implemented for high-risk populations in numerous cities across the country. This week alone, the New York City Department of Health launched 25,000 first-dose appointment slots for trans, gay, and bisexual men and their sexual networks.
The bad news: It’s hard to get a monkeypox vaccine right now, even for people who are eligible. “Vaccines against monkeypox are available, but on a limited basis, and the criteria for receiving a vaccine may vary depending on your risk status and where you live,” says Dr. Hirsch.
The case of a new disease outbreak and the confusion about access to the vaccine and the impact on your health can be really confusing, which is why some experts explain exactly what is happening with the monkeypox vaccine.
How does the monkeypox vaccine work?
We currently have two smallpox vaccines that are also effective against monkeypox: ACAM2000 and Jynneos, says Linda Yancey, MD, an infectious disease specialist at Memorial Hermann Health System in Houston. That’s because the monkeypox virus is a relative of the virus that causes smallpox; both are types of orthopoxviruses.
Jynneos is the newer of the two vaccines and has been around in the US since 2019. “The vaccine introduces a virus that doesn’t replicate to the immune system so antibodies can be produced against it.” Specifically, this vaccine uses a sample of a weaker, related orthopoxvirus. “Then when the person is exposed to the virus, they will be able to kill it quickly and prevent an infection,” says Dr. Yancey.
The oldest monkeypox vaccine is ACAM2000, which is an iteration of the vaccine used to eradicate smallpox in the 20th century. This vaccine uses a sample of a live, replicating virus called vaccinia to inoculate someone against smallpox. (More on the implications of that in a minute.)
These vaccines are highly effective at preventing monkeypox, about 85 percent, according to the CDC. They work best before exposure, but can also be used for post-exposure vaccination, says Dr. Yancey. “If given within four days of exposure, they can prevent illness. If given five to 14 days after exposure, they can lessen the severity of illness,” he says. This is a great feature of the vaccine because it offers a mechanism to prevent the spread of the disease once someone contracts it.
Eventually, when vaccine production ramps up, cities and towns will be able to take a public health measure called “ring vaccination.” This means that if someone gets monkeypox, everyone who lives with them or has been in close contact with them could be vaccinated to help prevent the spread.
What is the difference between the two monkeypox vaccines?
While both Jynneos and ACAM2000 use a live sample of the weaker vaccinia virus to help inoculate people, the version used in the older ACAM2000 virus can replicate. That has some implications for how these vaccines are given and who gets them.
To begin with, Jynneos is a two-dose injection into the arm, 28 days apart, while ACAM2000 is pricked into the skin with a double-pronged needle in a single dose. (The live virus causes a small pox to form on your arm, then blisters and falls off within a few weeks.) According to the CDC, it takes 14 days after the second dose of Jynneos for you to have a full immune response. It takes about four weeks for a person’s immune response to fully develop after receiving ACAM2000.
They also have different side effects. People may have pain or swelling at the injection site after receiving Jynneos injections, and the most common side effects are fatigue, headache, and muscle pain. ACAM2000 can also cause pain and swelling at the injection site, but is also associated with more serious (but rare) side effects such as myocarditis and pericarditis, also known as inflammation of the heart or lining of the heart.
But the biggest difference comes down to who can take which vaccine. If you’ve seen warnings about not getting a specific vaccine if you have psoriasis or eczema, ACAM2000 is what people are referring to, says Peter Lio, MD, FAAD, an assistant clinical professor of dermatology and pediatrics at the University Feinberg School of Medicine. Northwestern. and adviser to Gladskin. This is because the live virus that replicates in ACAM2000, while generally safe for most people, could harm people who have compromised immune systems (for example, who have cancer or HIV), are pregnant, or have inflammatory skin conditions such as eczema. (Jynneos is generally considered safer for these populations.)
However, don’t bother getting also caught in the thick of these vaccine differences. Why? Jynneos is the only one specifically approved by the FDA to fight monkeypox. (ACAM2000 can be used for monkeypox due to a specific FDA protocol that requires patients to complete an informed consent form.) The current vaccine distributed in cities like New York, San Francisco and Chicago is the Jynneos vaccine, explains Dr. Yancey. It’s also safer to distribute to people with compromised immune systems (essential, since 41% of confirmed monkeypox cases worldwide are in people who also have HIV). Dr. Lio says that Jynneos is safe for people with skin conditions and that monkeypox poses a much more serious risk to people with these conditions than the newer vaccine.
How to get the monkeypox vaccine if you are eligible
Unfortunately, this is the most difficult question to answer right now. Currently, the demand for the vaccine has far outstripped our supply, says Dr. Yancey. (There is a large stockpile of the ACAM2000 vaccine and only a small stockpile of Jynneos, but the federal government is working to address that as we speak.) There are more vaccines on the way, but it will be a while before we can give everyone a shot who wants or needs one.
The only way to get the vaccine, at the moment, is to be among at-risk populations (such as men who have sex with men and their close contacts) and purchase a dose through your local health department. “We anticipate that over time it will be more widely available, but right now, hospitals and doctors’ offices don’t have it,” says Dr. Yancey. Over time, this will expand to include immunocompromised and healthcare workers. Eventually, it will be available to the rest of the population if the outbreak continues.