What is it?

Monkeypox is a viral zoonosis (an infection spread from animals to humans). It is caused by a virus that belongs to the Orthopoxvirus genus (which also causes the variola virus responsible for smallpox disease and the vaccinia virus, which is used in smallpox vaccines). Monkeypox was first discovered in 1958 and there have been small outbreaks since, predominantly in Western and Central Africa. Since the eradication of smallpox in 1980, monkeypox has become the most important orthopoxvirus affecting humans, however, causes less severe disease than smallpox.

What to look for

The incubation period of monkeypox is usually 7-14 days, but can be as short as 5 days or as long as 21 days. The initial symptoms of monkeypox include fever, headache, backache and muscle aches, fatigue and lymphadenopathy. Lymphadenopathy in this early phase is a key feature of monkeypox.

1-3 days following the beginning of fever, a rash may develop, often beginning on the mouth and face, and then spreading to other areas of the body. The face is involved in 95% infections, followed by the palms of the hands and soles of the feed (75%). Oral mucous membranes are involved in 70% of cases, and involvement of the genitalia is also common (30%).

The rash is initially characterised as being erythematous (reddened) and macular (flat), which then develops papular features (raised areas) and turns into well-demarcated pustules and vesicles. These then dry into crusts and fall off. The number of lesions is highly variable, ranging from a couple to over a thousand.

The infection is usually self-limiting with symptoms lasting from 2-4 weeks. Complications can include secondary infection such as cellulitis, sepsis, infection of the cornea (which can be threaten vision), bronchopneumonia and encephalitis. The case fatality ratio is between 3-6%. More severe illness can occur in immunocompromised people.

How is it transmitted?

Monkeypox is spread via either animal-to-human transmission (zoonotic) or human-to-human transmission.

Zoonotic transmission involves direct contact with the bodily fluids, blood, or lesions (cutaneous or mucosal) of infected animals. This is most common for people living near or within forest areas with exposure to infected animals.

Human-to-human transmission involves close contact with respiratory secretions, the skin lesions of an infected person, or a contaminated objects such as linen or clothing. Droplet particle transmission requires prolonged face-to-face exposure, placing household contacts at highest risk. This can be minimised by isolating away from other members of the household.

Healthcare workers caring for individuals with monkeypox must undertake infection control precautions and handling of laboratory specimens should be by suitably trained staff.

Epidemiology

Monkeypox is very common in West and Central Africa, often in areas with tropical rainforests. However, there is currently outbreaks in many other countries across the globe including Australia and parts of Europe and the United Kingdom.

Vaccines

The vaccinia virus is a poxvirus related to smallpox and monkeypox and is contained in smallpox vaccines. Historically, smallpox vaccines have been used in the prevention of smallpox infection, however, they are also likely to be effective against monkeypox.

There are two types of smallpox vaccines available for use in Australia for the prevention of monkeypox:

  • ACAM2000™ – 2nd generation, live-attenuated vaccine
  • JYNNEOS® – 3rd generation, non-replicating vaccine

Recommendations

Either vaccine can be administered as either pre-exposure prophylaxis (PrEP) or post-exposure prophylaxis (PEP) based on an individual risk-benefit assessment. For PEP, vaccination within 4 days is recommended to provide optimal protection against the development of monkeypox infection. Vaccination between 4-14 days following exposure may lessen the severity of disease.

ATAGI preferentially recommends JYNNEOS® vaccine due to the ease of administration and decreased likelihood of side effects. Vaccination is currently recommended for the following groups:

  • GBMSM (gay and bisexual men who have sex with men) aged ≥ 16 years who are the highest risk of infection with monkeypox:
    • those living with HIV
    • recent history of multiple sexual partners, including group sex or sex on licensed premises
    • other markers including recent sexually transmitted disease or on HIV PrEP due to number of partners
    • recommendations from sexual health clinics
  • sex workers, particularly those with clients who belong to high-risk groups
  • anyone in the above categories planning to travel to a country experiencing a monkeypox outbreak
  • anyone at greater risk of poorer outcomes due to monkeypox infection, such as those with severe immunocompromise
  • immunisation providers who are administering ACAM2000™.

It is not currently recommended that all GBMSM are immunised, due to the current epidemiology, low risk of infection and limited vaccine supply.

Individuals who have a history of confirmed monkeypox infection should defer vaccination in the short-medium term after recovery due to the immunity gained from natural infection.

Precautions

Vaccination with JYNNEOS® can be considered in children aged < 18 years where the benefits of vaccination outweigh the risks of disease. Despite no formal studies, there are no theoretical safety concerns surrounding the administration of JYNNEOS® in pregnant or breastfeeding women.

Individuals receiving ACAM2000™ as PrEP should consider an interval of 4 weeks between vaccination and administration of COVID-19 vaccines due to the rare risk of myocarditis/pericarditis.

Contraindications

Anyone with a history of anaphylaxis to a previous dose of the vaccine to be administered or anaphylaxis to a component of the vaccine to be administered should not be vaccinated.  Due to the risk of vaccine associated disease, ACAM2000™ is contraindicated for those with immunocompromise or those who are pregnant.

Individuals with active eczema, atopic dermatitis or other exfoliative skin conditions should not receive ACAM2000™ due to the risk of developing eczema vaccinatum (a reaction to smallpox vaccination experienced by people with eczema/atopic dermatitis resulting in a severe rash and systemic illness).

§ Using alternate routes of vaccine delivering to complete a primary course is acceptable (eg, intradermal for dose 1 and subcutaneous for dose 2)
€ Intradermal administration is an alternate route of vaccination for pre-exposure prophylaxis. It is not preferred for the first dose of post-exposure prophylaxis and is NOT recommended in people with severe immunocompromise
£ Vaccination providers administering intradermally should ensure that they are appropriately trained in intradermal technique. Where a dose of intradermal vaccine is inadvertently administered subcutaneously, a repeat dose of 0.5ml should be administered subcutaneously as soon as possible to ensure that the vaccinee receives an appropriate level of protection
^ Percutaneous administration involves using a bifurcated needle and scarification technique requiring specialised training and accreditation
# for full aftercare instructions, refer the product information
¥ ACAM2000 is a live-attenuated vaccine and therefore as outlined above, it’s use is contraindicated in some patient groups. For a full list of contraindications and precautions refer to the ATAGI clinical guidance on vaccination against Monkeypox.

Following vaccination

Individuals receiving ACAM2000™ should be advised that 2-5 days after vaccination a papule will form at the injection site. This will progress to a vesicle (blister) then pustule (blister with pus) before scabbing and forming a permanent pitted scar. Individuals are recommended to cover the injection site with a gauze bandage secured with adhesive tape until scabbing occurs, noting that the wound is infectious until the wound dries up.

Common systemic side effects following vaccination with either vaccine include muscle aches, headache, fatigue and nausea. Localised side effects can include injection site itch, pain redness and swelling (and permanent scarring following ACAM2000™.

ACAM2000™ is also associated with a risk of myocarditis and pericarditis as well as other serious side effects noted here.

Where to access vaccines

In metropolitan Victoria, vaccination is predominantly available via the below select sexual health clinics.

Vaccination in regional Victoria can be accessed by contacting the closest local public health unit.

Local public health unit (LPHU) Email
Ovens Murray phu@awh.org.au
Barwon South West phu@barwonhealth.org.au
Gippsland/Latrobe phu@lrh.com.au
Goulburn Valley phu@gvhealth.org.au
Ballarat/Grampians phu@bhs.org.au
Loddon Mallee phu@bendigohealth.org.au

Alternatively, Victorians can register their interest in receiving a monkeypox vaccine here.

Resources

Authors: Rachael Purcell (RCH Immunisation Fellow), Francesca Machingaifa (MVEC Education Nurse Coordinator) and Rachael McGuire (MVEC Education Nurse Coordinator)

Reviewed by: Francesca Machingaifa (MVEC Education Nurse Coordinator) and Rachael McGuire (MVEC Education Nurse Coordinator)

Date: September 8, 2022

Materials in this section are updated as new information and vaccines become available. The Melbourne Vaccine Education Centre (MVEC) staff regularly reviews materials for accuracy.

You should not consider the information in this site to be specific, professional medical advice for your personal health or for your family’s personal health. For medical concerns, including decisions about vaccinations, medications and other treatments, you should always consult a healthcare professional.