Mpox is a disease caused by the monkeypox virus. In most people, mpox begins with general flu-like symptoms, followed by a blistering rash that can be painful. In some people, the rash is limited to one area of the body only. 

Some people can develop more severe mpox disease that needs to be managed in hospital. People with conditions that affect their immune system may be at greater risk of severe mpox. More information on the signs and symptoms can be found here.

Mpox is spread from person to person through contact with the mpox rash, especially contact with fluid from mpox blisters. This contact also includes sharing items like towels and linen, because the virus that has been shed from the skin of an infected person can remain on these objects for some time.

Mpox can also be spread through prolonged contact with respiratory secretions, such as saliva, of an infected person. This may occur through intimate physical contact, such as kissing or oral sex.

Pregnant women can also spread the virus to their unborn babies through the placenta. However, currently there have not been any known cases of mpox being spread through breastfeeding.

The main vaccine against mpox available in Australia is called Jynneos. Overseas, the identical product may be known by its other brand names, Imvanex and Imvamune. 

Jynneos can be administered via subcutaneous or intradermal injection. Your vaccination provider will discuss the best option for you. The same vaccines are used against mpox and smallpox. If you have never received a smallpox  vaccine in the past, two doses of Jynneos, given at least 28 days apart, will give the best protection against mpox. If you have received the smallpox vaccine more than 10 years ago, only 1 additional dose of Jynneos is needed this time.

There is limited supply in Australia of another vaccine called ACAM2000, but its use is reserved for specific circumstances, determined by State and Territory public health authorities.

Vaccines used against smallpox contain another virus, called the vaccinia virus, which is closely related to both the smallpox and the monkeypox viruses. It is believed that vaccines with the vaccinia virus will protect people against mpox in the same way that they protect against smallpox. Before the 2022 outbreak, there was already some evidence of this cross-protection. People who were vaccinated against smallpox in their childhood have been observed to have some protection against mpox many years later in isolated outbreaks in the Democratic Republic of the Congo.

Jynneos has been shown to be a safe vaccine, with more than a million doses given worldwide in the current 2022 mpox outbreak. 

AusVaxSafety is an Australian system that collects information on reactions after vaccination. Currently, most reactions reported after Jynneos have been mild and expected, such as pain and redness at the injection site that resolve within days. These injection site reactions are slightly more common after intradermal injections compared to subcutaneous injections. For more information on reactions observed after the Jynneos vaccine in Australia, visit the AusVaxSafety mpox vaccine website.

A range of systems, including AusVaxSafety and the Therapeutic Goods Administration, will continue to monitor the safety of the Jynneos vaccine.

Your local State or Territory will decide who can get the mpox vaccine based on the mpox situation in different parts of Australia, and this has been informed by the clinical guidance from the Australian Technical Advisory Group on Immunisation (ATAGI) on the population groups recommended to be prioritised for mpox vaccine.

The delivery of mpox vaccines is coordinated by each State and Territory. Contact the relevant State and Territory public health authority for the latest information on eligibility to receive vaccination, and how to access the vaccine if you are eligible.

Your vaccination provider will discuss the injection site with you. For subcutaneous injections, the most common site is the upper arm, below the shoulder. Intradermal injections are often given in the forearm, because we have the most information about the effectiveness of the vaccine given here. If this is not preferred, sites such as the upper arm and the upper back just below the shoulder blade are also used. If you prefer another body site, discuss with your vaccination provider whether this would be suitable.

Jynneos vaccine is not expected to interact with any medications given as part of HIV treatment or HIV pre-exposure prophylaxis. It is important to continue with any recommended HIV treatment if receiving a mpox vaccine for either primary prevention post exposure.

It is not yet known the antibody level where you would be considered to be protected against mpox. In clinical trials for Jynneos vaccine, antibody levels at various time points after vaccination were measured. After one dose of Jynneos vaccine, antibody levels reached their peak at approximately 2 weeks after vaccination, and then stayed at roughly this level. After the 2nd dose of Jynneos vaccine, 4 weeks after the first, antibody levels rose again and reached a higher peak, approximately 2 weeks after the second dose. This has led to the conclusion that the best protection against mpox occurs approximately 2 weeks after receiving the second dose of Jynneos vaccine.

Clinical studies have shown that the frequency of side effects after mpox vaccination is similar among people who had received a previous dose of a smallpox vaccine and those who were never vaccinated against smallpox. For people who have received a previous smallpox vaccine more than 10 years ago, and who have been recommended to receive Jynneos vaccine during the current mpox outbreak, only a single dose of Jynneos vaccine is required.

Receiving a vaccine after being in contact with somebody who is infected is called post-exposure preventive vaccination (PEPV). It is recommended for some people after they have had a high-risk exposure to a person with mpox. Depending on the timing and nature of this exposure, and a range of other factors, receiving 1 dose of the vaccine may be effective in preventing mpox, or reducing the severity of illness. We are still learning about the effectiveness of giving the Jynneos vaccine as PEPV. In general, it is thought that receiving the vaccine as soon as possible after the exposure, ideally within 4 days, would be more effective at preventing mpox.

It is important to discuss if you have had a potential exposure to a person who may have mpox with your State and Territory public health authority. They can give you advice about whether you might benefit from receiving the Jynneos vaccine, and if so, they can organise for you to be vaccinated.

It is important to contact your state/territory public health staff about your exposure as they can give you advice on what to do and link you with any care that you may need, including vaccination. A list of relevant phone numbers can be found here.

Any identified close contacts are advised to follow the isolation advice given to them by their local public health unit, regardless of whether they have received Jynneos vaccine as post-exposure prophylaxis.

Anyone who has received a dose of the Jynneos vaccine (it may have been branded as Imvanex or Imvamune, depending on the country) is advised to let their healthcare provider or sexual health service know, so that this dose can be recorded accurately. Additionally, you can discuss your ongoing risk of being infected with the monkeypox virus with your healthcare providers or sexual health clinician to determine if and when you should have a second dose of the vaccine.

It is possible for your Jynneos vaccine dose(s) to be recorded, but hidden on official print-outs like the Immunisation History Statement. You can discuss this with your immunisation provider at the time of receiving your vaccine or contact AIR at 1800 653 809.

The definition of severe immunocompromise, as applicable to smallpox/monkeypox vaccines, are now outlined in Appendix A of Version 4 of the ATAGI Clinical Guidance on vaccination against monkeypox.

If an individual becomes infected with mpox virus after their first dose of Jynneos vaccine, they do not need a second dose in the short to medium term, as infection with the virus will boost their natural immunity.

Given the uncertainty about the effectiveness of the pre-exposure dose received, consider giving a second dose of Jynneos vaccine as post-exposure preventive vaccination (PEPV) as soon as possible after the exposure, and consider giving an extra 3rd dose at least 28 days after the 2nd dose to complete the course. While the dose immediately post exposure should be administered subcutaneously, the 3rd dose 28 days later can be administered via either the subcutaneous or intradermal route.

In this case, the individual would be considered at a high risk of ongoing exposure to monkeypox virus and recommended to receive 2 doses of Jynneos vaccine. A risk assessment would need to be undertaken in liaison with the local public health unit to determine the timing of the 2nd dose.

If the second exposure is deemed as high risk by the public health unit, then given the uncertainty about the effectiveness of the pre-exposure dose received, consider giving a second dose as post-exposure preventive vaccination as soon as possible after the exposure. Also consider giving an extra 3rd dose at least 28 days after the 2nd dose to complete the course.

While the dose immediately post exposure should be administered subcutaneously, the third dose 28 days later can be administered via either the subcutaneous or intradermal route. It is also important to ensure that the individual has been given advice on the need to continue to take measures to reduce exposure, even after vaccination.

If the second dose was given less than 21 days after the first, repeat the second dose, ideally at least 28 days after dose 1 (therefore there would be a third, extra dose, at least 28 days after dose 1).

People with severe immunocompromise who had the smallpox vaccine many years ago are recommended to receive 2 doses of Jynneos vaccine, 28 days apart.

Yes, if possible, try to characterise the allergic reaction in more detail. If this reaction may have been anaphylaxis, refer the individual to a specialist immunisation service (SIS). The SIS can also give advice on other clinical concerns or arrange for Jynneos vaccine to be given in a supervised setting.

Note that the excipients in Jynneos vaccine are not the same as those in 1st and 2nd generation smallpox vaccines.
 

As the prevalence of antibodies against smallpox, mpox or vaccinia are expected to be currently low in the general population, recent receipt of blood products poses minimal theoretical risk of interference with the immune response to Jynneos vaccine. There are no additional precautions for giving Jynneos vaccine to recent recipients of blood products, nor is a delay needed.

If the individual has no other risk factors for myocarditis or pericarditis, other than being a younger male, Jynneos can be given at the same time as a COVID-19 vaccine. However, if there is additional clinical concern about myocarditis or pericarditis for a particular vaccine recipient, a 2-week interval between COVID-19 vaccine and Jynneos administration could be considered. If the risk of acquiring either disease is high or imminent, this interval could be shortened.

There are currently no data on whether co-administration of Jynneos vaccine and any other live vaccines would affect immune response to any of the vaccines given. As Jynneos vaccine is a non-replicating vaccine, it is less likely to impact on co-administered live attenuated vaccines.

For international travel, consideration needs to be given to the increased incidence of measles globally, and the yellow fever vaccine being a statutory requirement for many destinations. Therefore, co-administration of Jynneos vaccine and other live vaccines can be offered as an option, with appropriate counselling on the limitations of evidence available.

Jynneos is not expected to interact with any medications given as part of HIV treatment or HIV pre-exposure prophylaxis. It is important to continue with any recommended HIV treatment if receiving a mpox vaccine for either primary preventive vaccination or post-exposure preventive vaccination.

Primary preventive vaccination

It is not yet known how much protection 1 dose of the vaccine gives compared with 2 doses. In clinical studies, there was an antibody rise after a single dose of Jynneos vaccine, which suggests that there is some immune response to 1 dose. However, there was a higher level of antibodies after the 2nd dose. In the current global outbreak, a study from Israel has shown that among people at high risk of monkeypox virus infection, the effectiveness of one dose of the vaccine at less than 6 weeks of follow-up was estimated to be 79%.

Post-exposure preventive vaccination

We do not yet have a precise estimate of the effectiveness of one dose of Jynneos vaccine used as post-exposure prophylaxis. Historical evidence from using older-generation smallpox vaccines against smallpox indicates that the first dose of post-exposure vaccination is more effective if given as soon as possible after exposure.

The current guidance on the administration of Jynneos was based on a clinical study that showed similar immune responses to both intradermal and subcutaneous administration. 

However, there are no data on intradermal administration of Jynneos for severely immunocompromised people, nor for post-exposure preventive vaccination. Therefore, as a precaution, only the subcutaneous route was initially recommended for people with severe immunocompromise, and people requiring Jynneos for post-exposure purposes. 

In Version 4 of the ATAGI Clinical Guidance on vaccination against monkeypox, this recommendation is changed to reflect the global experience of using Jynneos in the 2022 MPX outbreak. People with severe immunocompromise are now recommended to receive Jynneos as primary preventive vaccination (PPV) via either the intradermal or subcutaneous routes. They still remain as a group that should be prioritised to receive their second dose at least 28 days after the first dose.

The risk of exposure, infection and serious outcomes in a pregnant woman or her fetus is best determined through an individual risk assessment, which may be undertaken in conjunction with the local public health unit.

Evidence on the risk of vaccination in pregnant women is limited. In clinical trials, fewer than 300 pregnant women received the MVA-BN (Modified Vaccinia Ankara - Bavarian Nordic) vaccine, with no safety concerns reported. In the current outbreak, there have been no suggestions that using Jynneos vaccine in pregnant women is associated with any additional adverse events for either the mother or the fetus.

Evidence on the risk of infection with monkeypox virus in pregnancy is also limited. Vertical transmission to the fetus has been documented, and may occur both during the pregnancy and around the time of delivery. A small case series from the Democratic Republic of Congo of four pregnant women diagnosed with mpox during the first or second trimesters reported that three of these pregnancies ended in miscarriage or stillbirth. In the current 2022 mpox outbreak, there have been 17 cases of mpox infection in pregnant women in the United States of America, and limited reports of nine additional cases in Brazil. No adverse outcomes to either the mother or the fetus have been reported in these cases to date, but many of these pregnancies continue to be monitored.

The dose administered intramuscular does not need to be repeated. However, consider advising the vaccinee about the increased likelihood of an injection site reaction.

While a bleb/wheal is usually present after a successful intradermal injection, the absence of a bleb/wheal does not mean that administration failed. Because of factors such as an individual’s skin type, sometimes a bleb/wheal does not form even though the vaccine was administered correctly.

If the dose was administered subcutaneously, and less than half of the vaccine dose was given, repeat the full dose as soon as possible. If more than half the dose was given, do not repeat the dose.

For an intradermal dose, if the full dose is not given, then it needs to be repeated as soon as possible. The ATAGI guidance on incorrect administration of an intradermal Jynneos dose should be followed, which states that another intradermal (0.1 mL) dose can be given if the immuniser is experienced in intradermal administration, or an additional 0.5mL subcutaneous dose (drawn from a new vial) should be given.

Yes, considerations about vaccinating travellers should take into account both high-risk destinations and high-risk activities.

It is recommended two doses be administered before travel, so the Jynneos vaccine course needs to commence around 6 weeks prior to travel. If the time available pre-departure is shorter (<4–6 weeks), a single dose will only be possible and the 2nd dose may need to be delayed until return. Individuals should be advised that protection following a single dose will be lower than after 2 doses.