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JYNNEOS Vaccine for Monkeypox Exposure Q&A

August 3, 2022

Related Materials: Latest CDC Monkeypox Health Alert ( | Latest California Monkeypox Health Alert | CDC Health Alert Network (HAN) | California Health AlertsMonkeypox Vaccination Information | Monkeypox Q&A

Updates as of August 3, 2022:

  • Added questions on priority populations, dose intervals, protection, and vaccine access.

The California Department of Public Health will update recommendations and information as the situation continues to evolve.


The Centers for Disease Control and Prevention (CDC) and the California Department of Public Health (CDPH) recommend that people aged 18 or older who are at high risk for monkeypox infection get vaccinated to reduce their risk of becoming sick. This includes people who have or may have been exposed to the monkeypox virus.

The JYNNEOS vaccine is approved by the U.S. Food and Drug Administration (FDA) to prevent both monkeypox and smallpox. Vaccination helps protect against monkeypox when given before or shortly after an exposure. This vaccine is currently available in the United States from the federal Strategic National Stockpile

At this time, the federal government has allocated a limited number of JYNNEOS vaccine doses to Californians. CPDH is working with local health departments to make these doses available to protect against monkeypox. 

Who is currently recommended to receive the JYNNEOS vaccine? 

At this time, the JYNNEOS vaccine is being prioritized for the following groups:

  • Post-Exposure Prophylaxis (PEP) for known close contacts of monkeypox cases who are identified by public health via case investigation, contact tracing, and risk exposure assessments.
  • Post-Exposure Prophylaxis (PEP)++ for individuals with certain risk factors who are more likely to have been recently exposed to monkeypox even if they have not had documented exposure to someone with confirmed monkeypox.
  • Pre-Exposure Prophylaxis (PrEP) for individuals at occupational risk of monkeypox according to Advisory Committee on Immunization Practices (ACIP) guidance, including laboratory workers who perform monkeypox testing, and clinical and public health workers who collect monkeypox specimens.

How is the JYNNEOS vaccine given?

Like other vaccines, the JYNNEOS vaccine is given by injection, typically in the upper arm. The CDC recommends that people get two doses, at least four weeks apart. CDPH recommends that people who are moderately to severely immunocompromised should receive the second dose of the JYNNEOS vaccine 4 weeks after their first dose.
While supplies remain scarce, people who are not immunocompromised may receive their second JYNNEOS dose at an interval greater than 4 weeks after their first dose.

Why is CDPH making a recommendation for a longer interval between the first and second JYNNEOS doses? 

As of July 2022, the federal government has allocated a limited number of JYNNEOS vaccine doses to California. Unfortunately, the current supplies of JYNNEOS vaccine are expected to be insufficient to protect all people who might be at risk of contracting monkeypox during the current outbreak. To reach the greatest number of people, CDPH is recommending prioritizing first doses of JYNNEOS vaccine to persons at high risk of monkeypox infection. CDPH anticipates additional doses from the federal government in the coming months and that second doses will be made available more broadly at that time. Increasing the interval between doses is not expected to reduce the level of immunity after a second dose. 

How protected am I after getting the JYNNEOS vaccine?

We have some information about monkeypox protection from the JYNNEOS vaccine but will be learning more during the current outbreak of monkeypox. 

The JYNNEOS vaccine was approved by the FDA based on clinical trials limited data from animal model studies indicate that a single dose of JYNNEOS might provide protection against monkeypox infection in some persons. 

Because monkeypox is rare, it has not been possible to test how well the JYNNEOS vaccine prevents infection in a real-world setting. In addition, there is not yet information on the effectiveness of the JYNNEOS vaccine in the current outbreak. Vaccinated persons are still recommended to take additional measures to protect themselves against catching or spreading monkeypox and to isolate at home when they have a rash or other symptoms. 

When am I considered fully vaccinated with JYNNEOS vaccine?

Individuals are considered fully vaccinated 2 weeks after receiving their second dose of the JYNNEOS vaccine. While individuals with one dose of the vaccine are not considered fully vaccinated, there is some evidence to suggest that these individuals still get some protection with one dose of the vaccine. Because they may not be completely protected, vaccinated individuals are still recommended to take additional measures to protect against catching or spreading monkeypox and to isolate at home when they have a rash or other symptoms until they have confirmed whether or not they have monkeypox.

When may JYNNEOS vaccine be given after an exposure?

JYNNEOS vaccine should be given within 4 days from the date of exposure, if possible, to help prevent onset of the disease. If given between 4–14 days after the date of exposure, vaccination may reduce the symptoms of disease, but may not prevent the disease. If monkeypox symptoms have already occurred, JYNNEOS vaccine is not recommended.

Who should NOT receive the JYNNEOS vaccine?

People who have had a serious allergic reaction to a previous dose of the JYNNEOS vaccine or a component in the vaccine should talk to their health care provider to see if it is safe to receive the vaccine.

While you may still be able to be vaccinated with JYNNEOS if you have the following conditions, please tell your vaccination provider if you:

  • Have any severe, life-threatening allergies
  • Are pregnant or think you may be pregnant
  • Are breastfeeding
  • Have a weakened immune system 

May I get JYNNEOS vaccine if I am pregnant or might be pregnant? 

Pregnancy is not a contraindication to immunization with JYNNEOS vaccine for individuals exposed to monkeypox. However, data on the risks of JYNNEOS vaccination during pregnancy are limited. Monkeypox infection during pregnancy is associated with complications, including severe congenital infection, pregnancy loss, and maternal mortality. Individuals should discuss risks and benefits of vaccination related to their risk of exposure to monkeypox infection with their healthcare providers.

May I get JYNNEOS vaccine if I am breastfeeding?

Lactation is not a contraindication to immunization with JYNNEOS vaccine for individuals exposed to monkeypox. It is unknown whether JYNNEOS is excreted in human breast milk. Data are not yet available to assess the effects of JYNNEOS in a breastfed infant or on milk production. However, because JYNNEOS vaccine does not contain a virus that replicates, it likely does not present a risk of transmission to breastfed infants. Healthcare providers should discuss the risk and benefits with the patient using shared decision making.

What are the side effects of JYNNEOS?

Most people who get the JYNNEOS vaccine have minor reactions. These may include pain, redness, swelling, firmness, or itching where the shot was given. You also may have muscle pain, headaches, nausea, chills, or may feel tired. There is a small chance of fever. As with any medicine, there is a very small chance of a vaccine causing a severe allergic reaction.

What if I have a severe allergic reaction?

If you have signs of a severe allergic reaction (such as hives, swelling of the face or
throat, difficulty breathing, a fast heartbeat, or dizziness), call 911 immediately or go to the nearest hospital. For other concerns, contact a health care provider.

Adverse reactions should be reported to the Vaccine Adverse Event Reporting System (VAERS). Your health care provider will usually file this report, or you can do it yourself. Visit the VAERS website or call 800-822-7967. VAERS is only for reporting reactions, and VAERS staff members do not give medical advice.

You can visit the FDA website (PDF) to read the package insert for this vaccine. For more general information on monkeypox, visit the CDPH Monkeypox website. For more information on the vaccine, visit the CDC JYNNEOS Vaccine Statement (PDF) and the CDC's Consideration on Monkeypox Vaccine site.  

How can I get the vaccine?

Contact your health care provider to see if you are currently in one of the recommended groups for receiving the JYNNEOS vaccine. JYNNEOS vaccine supply is still extremely limited and only available via public health distribution from the federal Strategic National Stockpile. If vaccine is recommended for you, your healthcare provider can consult with local public health department(s) to identify locations near you that may have vaccine to administer.

Which healthcare workers should be vaccinated against monkeypox?

Current evidence shows that the risk for transmission of monkeypox to healthcare workers (HCWs) is low. While supplies of vaccine continue to be limited, CDPH recommends prioritizing vaccination to persons at risk in the community from their exposures outside of healthcare settings.

Current CDC infection control recommendations for healthcare facilities, including use of personal protective equipment (PPE), should be followed. PPE is readily available in healthcare facilities and is expected to be extremely effective at preventing transmission of monkeypox.    

CDPH recommends ACIP guidance for vaccination of the following HCWs:

  • Research laboratory personnel working with orthopoxviruses
  • Clinical laboratory personnel performing diagnostic testing for orthopoxviruses
  • Health care worker response teams designated by appropriate public health and antiterror authorities.
CDPH does not recommend vaccination of most HCWs. There can be consideration to immunizing a limited group of healthcare workers who will be routinely and frequently caring for persons with monkeypox infection. This decision to immunize should be made in collaboration with your local health department.

​​Originally published on July 20, 2022
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