Japanese encephalitis: What you need to know about vaccines for the mosquito-borne virus

For a long time, vaccination against the Japanese encephalitis virus has mostly only been available through travel doctors, for people heading overseas.

But now that cases have been detected in southern parts of Australia for the first time, the federal government is expanding its vaccination program.

For most people, the virus will be mild. About 99 per cent of people who get infected will have very mild or no symptoms. But for the small number who do develop severe encephalitis — an inflammation of the brain — it can be deadly.

So should you consider getting vaccinated against this virus, and what vaccines are available?

Who can get the vaccine?

Before the recent cases in southern Australia, the vaccine was mostly recommended for people travelling to Asia or the Torres Strait.

People who worked with animals could also choose to get vaccinated, but it wasn’t cheap.

JEV can be spread by some types of mosquito.(Pixabay)

Now the federal government is targeting priority, “high risk” groups, including:

  • workers at piggeries, pork abattoirs, or pork-processing plants
  • people who live at or need to visit one of those locations
  • workers who deal directly or indirectly with mosquitoes
  • laboratory workers who may be exposed to the virus.

The vaccine will be free for those groups, and the government is also purchasing 130,000 JEV vaccines — additional to the 15,000 already in Australia — that will be available from late March into April.

Should I get vaccinated for the virus if I’m not in a ‘high-risk’ group?

There is no recommendation for the general population to get vaccinated against this virus.

However Associate Professor Lara Herrero, a virology research leader at Griffith University, said it was important to monitor the virus’s spread in case the priority groups needed to change.

“It’s probably too early to make a blanket statement of whether or not the whole population should be vaccinated,” Dr Herrero said.

“At this point, I think the correct strategy would be to go with high risk groups and then as the situation evolves, we would reassess and make the required recommendations.”

Infectious diseases physician Paul Griffin said he did not think the general population needed to consider getting vaccinated yet, because for most people, the risk was very small.

“If we start to see cases outside of those very high-risk settings, then perhaps our vaccination rollout might expand to those areas, but that’s actually pretty unlikely,” he said.

“It’s not something that people in the general community need to be worried about right now.”

What vaccines are available for Japanese encephalitis virus, and which vaccine is best?

The two JEV vaccines available in Australia are Imojev (Sanofi-Aventis Australia) and JEspect (Seqirus).

Imojev is a single-dose, live-attenuated vaccine — which means it contains a weakened version of the virus.

A box showing Imoojev vaccine with a syringe in the foreground.
Imojev is one of two JEV vaccines available in Australia.(Supplied)

Dr Herrero said its advantages included being “highly efficacious” and offering about five years of protection.

On the flip side, it’s not suitable for pregnant women or people who are immunocompromised.

It also has to be kept cold, which can make storing and transporting it tricky.

JEspect only offers full protection after two doses, but is suitable for most people who cannot receive the Imojev vaccine.

It is an inactivated vaccine, which means it is more stable at room temperature and easier to store and maintain.

https://www.abc.net.au/news/2022-03-17/what-vaccines-are-for-japanese-encephalitis-mosquito-virus/100914136