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Monkeypox Vaccination: What to Know

Medically Reviewed by Dan Brennan, MD on August 01, 2022

Monkeypox is a viral infection caused by the monkeypox virus. It’s a milder, less serious relative of the virus that causes smallpox. If you’ve been exposed to it, within 3 weeks you’ll notice flu-like symptoms along with a rash that might look like pimples or a blister.

There’s no specific treatment or cure for monkeypox. But studies show smallpox vaccines can provide some protection against monkeypox. The FDA has approved two smallpox vaccines, Jynneos and ACAM2000, that might help prevent monkeypox. The vaccine is most effective if you take it before or soon after exposure to the virus.

Here’s a quick guide on the monkeypox vaccination, who needs it, when to take it, and what you can expect.

Monkeypox Vaccines: Jynneos and ACAM2000

Monkeypox can spread through close contact, often skin-to-skin, with an infected person or an animal. To control the current outbreak and slow the spread, the FDA has approved two vaccines:

Jynneos. Also called Imvamune or Imvanex, the vaccine contains a live vaccinia virus that’s designed to prevent infection for those who are at high risk for monkeypox. It’s a two-dose vaccine that you’ll take 4 weeks apart. The injection is given under the skin and usually doesn’t cause a reaction. It takes about 14 days after the second dose for your body to build a strong immune response to the virus.

The FDA approved this vaccine in 2019 for people who are 18 or older. If you’ve had the smallpox vaccine in the past, you might only need one dose. Jynneos is safe to use if you have HIV. It’s also safe if you have eczema or other skin conditions, or of you have any other conditions that weaken your immune system.

ACAM2000. Originally used against the smallpox virus, this vaccine contains a live virus that can multiply. It’s given as a prick on your skin. The person giving you the vaccine will dip a two-pronged steel needle into the vaccine solution and poke a spot on your upper arm several times.

A small lesion or a red, itchy bump (called “a take”) may form at the injection site after 3-4 days, and the virus can grow from here. It usually takes about 6 weeks for the lesion to heal, and it may leave you with a small scar. Take care not to touch the lesion. After you get the vaccine, it takes about 4 weeks for your body to build an immune response to the virus.

Who Should Get the Monkeypox Vaccine?

The CDC recommends vaccines for people who have been exposed to monkeypox or those who are more likely to get it.

This includes:

  • If you’ve come in close contact with someone who has monkeypox
  • If you’ve had sex with someone in the past 2 weeks who has tested positive for monkeypox
  • You’ve had multiple sexual partners in the past 2 weeks in an area with a monkeypox outbreak
  • If you work in a lab and handle samples or animals with orthopoxvirus
  • Health care workers

When Can You Get the Vaccine?

While it’s best to get the vaccine before you're exposed to monkeypox, getting it afterward may still help prevent the disease or make the symptoms less serious. Experts call this prophylaxis.

Vaccine strategies for monkeypox include:

Post-exposure prophylaxis (PEP). If you’ve been exposed to monkeypox, the CDC recommends getting a vaccine within 4 days from the date of exposure for the best results. This will prevent the virus from multiplying.

You can get the vaccine between 4-14 days after exposure before symptoms develop. But it won’t be as effective. It may reduce the serious symptoms, and it might be able to prevent an infection. In some cases, you could get it after 14 days, especially if you’re more likely to get a severe infection and your immune system isn’t as strong due to other illnesses.

But studies show that if you start to have symptoms, a vaccine may not protect you.

Post-exposure prophylaxis (PEP)++ after an outbreak. If you have certain risk factors that make you more likely to get monkeypox, you may get this vaccine even if you’ve not been around someone who has tested positive.

Pre-exposure prophylaxis (PrEP). This vaccine strategy is used for those who are at high risk for exposure. This can include lab, health care, and public health workers.

Where Can You Get Monkeypox Vaccines?

In the U.S., both vaccines can be found at the Strategic National Stockpile (SNS). It’s a network of locations within the country and contains a vast stock of medical supplies like antidotes and vaccines. They’re in charge of supplying your local public health agencies with supplies if there’s a national medical emergency or during an outbreak.

The U.S. has a limited supply of monkeypox vaccines. If you’re at risk for monkeypox or if you’ve been exposed to someone who tested positive, tell your doctor. They can give you a vaccine if you’re eligible for one.

If you’re under 18, your doctor will have to consult with the CDC before they can give you a vaccine.

Does the Monkeypox Vaccine Cause Side Effects?

Both vaccines can cause reactions where the needle enters your skin, such as:

  • Pain
  • Swelling
  • Redness
  • Itching

If you got Jynneos, side effects can also include fever, headaches, and muscle pain.

If you got ACAM200, side effects could include:

  • Fever
  • Rash
  • Lymph node swelling
  • Myocarditis (swelling of the heart muscle)
  • Pericarditis (swelling of the sac-like tissue around the heart)

If you notice these side effects after you leave the clinic, let your doctor know immediately.

Who Shouldn’t Get The Monkeypox Vaccine?

The monkeypox vaccine isn’t suitable for everyone.

Avoid ACAM2000:

  • For infants less than 12 months of age
  • If you had congenital conditions (at birth)
  • If you have a weakened immune system from conditions like HIV or AIDS
  • If you have eczema or other skin conditions that cause you to shed the top layers of your skin fast
  • If you are pregnant
  • If you have heart disease
  • If you use topical steroid medication for eye disease

You should take precautions before you get Jynneos if you:

  • Have had a severe allergic reaction (anaphylaxis) to chicken or egg protein
  • Have had Stevens-Johnson syndrome (SJS). It’s a rare, serious skin condition.
  • Have had toxic epidermal necrolysis (TEN). It’s a deadly condition that causes skin to peel and cause blisters. It’s usually caused by a drug reaction.

After you get the vaccine, it’s best to wait for 30 minutes to see if you have any reaction to it. If you have an allergic reaction, tell your doctor about it. If it’s a medical emergency, call 911 or go to the nearest hospital.

Show Sources

SOURCES:

CDC: “Considerations for Monkeypox Vaccination,” “Smallpox/Monkeypox VIS,” “Vaccines,” “Monkeypox and Smallpox Vaccine Guidance.”

WHO: “Multi-country monkeypox outbreak in non-endemic countries.”

Johns Hopkins Medicine: “Toxic Epidermal Necrolysis.”

FDA: “ACAM2000 (Smallpox Vaccine) Questions and Answers.”

U.S. Department of Human and Health Services: “Strategic National Stockpile (SNS).”

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