Australia only has one vaccine available that protects against the monkeypox virus, but not everyone needs it.
Now that the World Health Organization has declared the spread of monkeypox a global health emergency, here’s what we know about the vaccine and who should be vaccinated.
What vaccine is available?
A smallpox vaccine, ACAM2000, is registered for use in Australia and has the advantage of also protecting against monkeypox. The supply of this vaccine is available to the states and territories through the national medical stock.
Another smallpox vaccine, known under the names Jynneos, Imvanex and Imvamune, is available in other countries, including the US and UK, but is not currently registered or available for use in Australia.
With more than 70 countries affected by monkeypox outbreaks, this newer vaccine is also in short supply. Community health groups are working with the government to facilitate access as soon as possible, especially for high-risk and immunocompromised groups.
Not everyone needs vaccination
Most healthy people recover from monkeypox within a few weeks, experiencing symptoms such as fever, headache, muscle aches, back pain, swollen lymph nodes, chills, and exhaustion. In some cases, monkeypox may start with a rash or sores on the mouth and face, which can then spread to other parts of the body.
Serious illness and death are a risk in rare cases, especially in immunocompromised people.
ACAM2000 protects against monkeypox. But according to the Australian Technical Advisory Group on Immunization (Atagi), the vaccine cannot be used in severely immunocompromised people as it can cause rare but serious side effects. This makes the protection of the most vulnerable complicated. Pregnancy should also be avoided for 28 days after vaccination.
The good news is that monkeypox does not spread easily between people. To be at risk, you need close contact with lesions, body fluids, or respiratory droplets through prolonged face-to-face contact with an infected person.
With a low number of cases in Australia, contact tracing is simple and the risk of infection is lower, but high-risk communities are on particular alert. Until at least the end of November, monkeypox is a notifiable disease in Australia, meaning all cases must be reported to health authorities.
Who should get the vaccine?
Currently in Australia, ACAM2000 is recommended for healthcare workers who provide vaccination to others and who have not received a smallpox vaccine in the past. Healthcare workers who may see patients with monkeypox, along with laboratory workers who work with smallpox virus or monkeypox, may also consider vaccination.
Close contacts at high risk of monkeypox cases, such as household contacts and healthcare workers, are also offered on a case-by-case basis.
According to Atagi, giving the vaccine to someone exposed to the virus can prevent the disease from developing. “Vaccination within four days of first exposure to an infectious case will provide the greatest likelihood of disease prevention,” says Atagi.
How does ACAM2000 work?
The vaccine is made from a virus called vaccinia, which is a type of smallpox virus related to smallpox and monkeypox, but which does not cause either disease, and is also much milder than both viruses.
Administering the vaccine requires special training.
The skin is scratched repeatedly with a needle dipped in the vaccine. The virus begins to grow at the injection site, causing a red, itchy sore spot or “pock” in the days afterward. It then eventually blisters and scabs, and may leave a small scar.
The vaccine stimulates the immune system to develop antibodies that can help the body recognize and fight an infection if exposure to monkeypox occurs.
There is a risk that the vaccine virus will be transmitted from the wound site to your close contacts. People who are severely immunocompromised, pregnant, or have eczema are at greatest risk and may experience serious adverse events. The risk of transmission can be reduced by covering the injection site and good hygiene. The site is infectious until it runs out.
The Jynneos/Imvanex/Imvamune vaccine does not carry the same risk and can be used in immunocompromised people. It is given in two doses four weeks apart, although people who have been vaccinated in the past only need one dose.
I got a smallpox vaccine as a child. Am I still protected?
A systematic review published in 2019 suggests that the protection afforded against the smallpox virus can last more than 20 years after vaccination. A separate small study found that protection can last 35 years or more. Protection against monkeypox is expected to last the same way.
According to Atagi: “Infant smallpox vaccination may confer a longer-lasting immune response than vaccination during adulthood, but this is uncertain. Those who have previously received a smallpox vaccine are likely to have some residual protection and currently revaccination with ACAM2000 is not recommended. This advice may change if new vaccines become available.”