Aug 5, 2022 - Health

What you need to know about the monkeypox vaccine

Monkeypox vaccine is displayed by a medical professional.

Monkeypox vaccine is displayed by a medical professional. Photo: James Carbone/Newsday RM via Getty Images

The United States has declared a public health emergency for monkeypox, raising awareness of the outbreak hitting more than 70 countries across the world.

The big picture: Two-thirds of Americans said in a survey from the Annenberg Public Policy Center that they don't think there's a vaccine for monkeypox or they aren't sure. But there is and here's what you need to know about it.

Is there a vaccine for monkeypox?

There are two vaccines that are used to prevent monkeypox infections, per the Centers for Disease Control and Prevention.

  • The Jynneos vaccine, manufactured by the Danish company Bavarian Nordic, has been approved by the Food and Drug Administration to prevent monkeypox.
  • ACAM2000, which comes from the company Sanofi Pastuer Biologics, has been approved by the FDA for use against smallpox infection and for monkeypox under an expanded access application, the CDC said. ACAM2000 is found to have more side effects and a higher rate of adverse events.

Both vaccines are smallpox vaccines, which are believed to be effective at preventing monkeypox.

Worth noting: There is currently a limited supply of the Jynneos vaccine. The United States has been placing orders for the vaccine to handle the growing demand for vaccination, health officials told reporters Thursday.

  • The ACAM2000 has a larger supply of vaccines available, but the CDC does not recommend them for people with certain health conditions.

How many shots do the Jynneos vaccine and ACAM2000 require?

  • Jynneos vaccine requires two shots. The immune response takes 14 days after the second dose, the CDC said.
  • ACAM2000 has one dose. It takes four weeks for the immune response to reach maximum strength, per the CDC.

Differences between Jynneos vaccine and ACAM2000

The Jynneos vaccine includes a live virus that doesn't replicate and is associated with fewer adverse effects, the CDC said.

  • Health care providers are more comfortable distributing the vaccine, too, since it's given through needle injection.
  • The CDC says boosters are recommended every two years.

But ACAM2000 is distributed by multiple punctures, leading to potential scarring. The stainless steel needle is dipped into a reconstituted vaccine — a method often used for orthopoxvirus vaccinations, the CDC said.

  • The vaccine contains a virus capable of transmission to close contacts.
  • ACAM2000 has also been associated with side effects, like myocarditis.
  • Health officials recommend boosters for this vaccine every three years.
  • This vaccine is derived from Dryvax, which was previously used to eradicate smallpox.

How effective is the monkeypox vaccine?

Several observational studies found the smallpox vaccine is 85% effective in preventing monkeypox, the World Health Organization said.

  • Those who have had prior smallpox vaccination may have a milder case of monkeypox.

However, this is based on research from the 1980s based on a monkeypox outbreak in the Democratic Republic of Congo.

  • A similar study from the 1990s found 15% of 84 people with monkeypox had been previously vaccinated against smallpox, too, according to the CDC.

Heinz Weidenthaler, vice president of clinical strategy at Bavarian Nordic, which makes the Jynneos vaccine, told MIT Technology Review that animal studies found the vaccine offers “80 to 100%” protection against the disease.

  • It's hard to understand how effective the vaccines are for humans since it hasn't been tested on them, he said.

Worth noting: The CDC said there is no data available for the effectiveness of the vaccines for the current monkeypox outbreak.

How does the vaccine work?

The Jynneos vaccine contains a live weakened virus related to monkeypox and smallpox that does not replicate within the human body, per the CDC. You cannot catch monkeypox or smallpox from the vaccine, New York state health officials said.

  • It is delivered in two 0.5 millimeter doses under the skin 28 days apart.
  • The CDC recommends giving the vaccine between four and 14 days after exposure.
  • Vaccination may reduce symptoms, which begin one to two weeks after infection, but it may not prevent the disease entirely, per the CDC.

The ACAM2000 vaccine contains a live version of the Vaccinia virus that is replicated, allowing your body to develop immunity.

  • It is delivered in one dose through multiple punctures with a bifurcated needle, which is often used for smallpox.

What are the monkeypox vaccine's side effects?

For the Jynneos vaccine, adverse reactions include pain, swelling and redness at the spot of injection, according to the CDC.

  • Fatigue, headaches and muscle pain are similar reactions from the vaccine's clinical trials.

The ACAM2000 monkeypox vaccine has similar physical side effects from the shot but comes with a higher risk of adverse effects, including myocarditis and/or pericarditis, the CDC said.

  • ACAM2000 will be made available for those if their health care physician says the risks of monkeypox outweigh the risk of the vaccine's side effects, per the CDC.

Who is eligible to get the monkeypox vaccine?

The CDC has limited eligibility for those who want a monkeypox vaccine.

  • The current CDC recommendations include those who have been in close contact with someone infected with monkeypox and those who had multiple sex partners in the last two weeks within an area with a high number of confirmed cases.
  • Having a high number of sexual partners is not enough to get you a vaccine since it is not a sexually-transmitted disease.
  • Men who have sex with men and their sexual partners are considered higher risk currently.
  • The United States has enough vaccines on hand to treat a third of the near 1.6 million gay and bisexual men who are considered at high-risk, Axios previously reported.
  • The U.S. likely needs 3.2 million total doses to cover the at-risk population, J. Stephen Morrison, director of the Global Health Policy Center at the Center for Strategic and International Studies, said on a recent podcast.
  • Monkeypox vaccines may not be readily available for at-risk Americans if cases continue to rise, the Washington Post reports.

What's next: U.S. health officials said Thursday that nearly 800,000 monkeypox vaccine doses will be made available soon for distribution

  • But some hotspot states where monkeypox is surging have seen a disconnect between how many doses are needed and how many have been allotted.
  • The U.S. will receive another 150,000 monkeypox vaccine doses in the strategic national stockpile in September, health officials told reporters Thursday. These doses were previously scheduled to arrive in October.

Go deeper ... 1 in 5 Americans fear they'll get monkeypox

Go deeper